Morbidly adherent placenta (placenta previa and placenta accreta spectrum): clinical guidelines

List of Abbreviations

Terms and Definitions

Placenta previa is a condition where the placenta completely or partially covers the internal os of the uterus [1]. In placenta previa, the placenta lies in the path of the delivering fetus ("prae" – "in front of", "via" – "on the way").

Low-lying placenta is a condition where the placenta is located within 20 mm of the internal os of the uterus, but does not cover it [2,3].

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Placenta accreta spectrum is abnormal trophoblast invasion of part or all of the placenta into the myometrium of the uterine wall [4].

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

The etiology and pathogenesis of placenta accreta remain incompletely understood. The primary cause of placenta accreta and placenta previa is considered to be endometrial atrophy resulting from invasive intrauterine procedures and/or inflammatory processes of the endometrium [4].

The most relevant theory of the pathogenesis of placenta accreta and placenta previa is based on deficiency of the endometrial decidual layer, which fails to halt the invasion of placental tissue [4]. Pregnancy initiates an increase in uterine blood flow, but the area of scarred myometrium is incapable of providing adequate blood supply. Decreased vascularization around the defect occurs due to the replacement of connective tissue with fibrous tissue, leading to local ischemia and focal degeneration [5].

It can be hypothesized that the pathophysiological basis of placenta accreta is myometrial fibrosis, which initiates necrosis of vessel walls. This process leads to the prolapse of chorionic villi into the vascular lumens and the formation of vascular lacunae and neovessels [6].

Risk factors for placenta accreta:

• Uterine scar. The risk increases with a higher number of previous cesarean deliveries [4,7–9]. The incidence of placenta accreta in patients with a history of 1, 2, 3, 4, and 5 abdominal deliveries is 3%, 11%, 40%, 61%, and 67%, respectively [10]. No correlation has been found between the depth of chorionic villi invasion and the number of previous cesarean sections [2]. No statistically significant association has been identified between the time interval since abdominal surgical delivery and the future risk of placenta accreta [11]. Elective cesarean section is associated with a lower probability of developing placenta accreta in the future compared to emergency cesarean section. (The probability of placenta accreta in the future is higher after an emergency CS than after an elective one) [12].

• Uterine scar following a cesarean section combined with placenta previa in the current pregnancy [8,13,14]. The combination of a uterine scar from a previous cesarean section and placenta previa in the current pregnancy is associated with an increased risk of placenta accreta [13].

• Pregnancy within a prior cesarean scar in early gestation or a history of myomectomy is associated with placenta accreta later in pregnancy [15].

• Intrauterine procedures (curettage, endometrial ablation, manual exploration of the postpartum uterine cavity), pelvic inflammatory disease, uterine artery embolization, submucosal leiomyoma [2]. Asherman syndrome, congenital uterine malformations, history of chemotherapy and radiation therapy, chronic endometritis, advanced reproductive age, smoking [16].

Risk factors for placenta previa:

• Cesarean section is associated with an increased risk of placenta previa in subsequent pregnancies. This risk increases with the number of cesarean sections. The incidence of placenta previa increases from 10 per 1,000 deliveries after one cesarean section to 28 per 1,000 deliveries after 3 or more cesarean sections.

• Assisted reproductive technologies and smoking increase the risk of placenta previa.

• Multiple pregnancy increases the risk of placenta previa, with monochorionic twins carrying a higher risk than dichorionic twins compared to singleton pregnancies [1,17,18].

1.3 Epidemiology of the Disease or Condition

In recent decades, there has been a steady increase in the incidence of placenta accreta, rising from 1 in 4,000 deliveries in 1970 to 1 in 533 today, driven by the increasing rate of surgical deliveries [19]. The incidence of placenta previa with and without hemorrhage in 2020 was 1.66 and 4.33 per 1,000 deliveries, respectively [1]. The prevalence of placenta accreta is 14.1 per 10,000 deliveries in Canada, 1.7 per 10,000 in the UK, and 4.8 per 10,000 deliveries in Hong Kong [4]. Currently, placenta accreta is the leading cause of obstetric hysterectomy worldwide, accounting for 38% of cases [20,21].

[1] "Key indicators of maternal and child health, and the performance of child and maternity healthcare services in the Russian Federation", 2021.

1.4 Features of Coding the Disease or Condition

Class XV: Pregnancy, childbirth and the puerperium;

Block (O30-O48) Maternal care related to the fetus and amniotic cavity and possible delivery complications:

O43. Placental disorders;

O43.1. Placental anomaly;

O43.2 Placenta accreta;

O44.0 Placenta previa specified as without hemorrhage;

O44.1 Placenta previa with hemorrhage.

1.5 Classification of the disease or condition

Placenta previa

• Placenta previa is a condition where the placenta completely or partially covers the internal os of the uterus.

• Low-lying placenta is a condition where the placenta is located ≤ 20 mm from the internal os of the uterus, but does not cover it.

The diagnosis of "placenta previa" or "low-lying placenta" is established after 16 weeks of gestation. If the placental edge is located > 20 mm from the internal os of the uterus, placental location is considered normal.

This classification has been adopted by all leading global organizations and is based on assessing the risk of perinatal complications, such as antepartum hemorrhage and massive postpartum hemorrhage, as well as aimed at improving obstetric management in patients with placenta previa.

The probability of bleeding is higher when the placental edge is located within 2 cm of the internal cervical os in the third trimester. A placental edge location of ≥ 2 cm from the internal cervical os does not increase the risk of antepartum hemorrhage and cesarean section [1,3,22].

Placenta accreta

There are three morphological variants of impaired chorionic villous invasion:

• adherence to the myometrium – placenta accreta

• invasion into the myometrium – placenta increta

• invasion through the serosa and/or adjacent organs – placenta percreta [10].

FIGO placenta accreta spectrum (PAS) classification [23].

Topographic classification of placenta accreta [24].

Type 1 – invasion of the uterine serosa, involvement of the dome and posterior wall of the urinary bladder with involvement of the superior vesical and uterine arteries.

Type 2 – invasion of the parametrium with involvement of the uterine, ureteral, and obturator arteries.

Type 3 – invasion of the cervix and vagina with involvement of the vaginal and cervical arteries.

Type 4 – invasion of the cervix and vagina with fibrotic changes between the uterus and urinary bladder.

1.6 Clinical presentation of the disease or condition

Placenta previa/accreta have no pathognomonic clinical signs. At term pregnancy, a high-standing presenting part may be observed. The main manifestation is uterine bleeding during pregnancy, labor, or cesarean section. Placenta accreta is characterized by the inability to spontaneously or manually separate the placenta from the uterine wall [4,25,26].

2. Diagnostics, medical indications and contraindications for diagnostic methods

2.1 Complaints and Anamnesis

Comment: The following complaints must be taken into account: genital spotting, abdominal pain.

In the medical history, pay attention to: invasive intrauterine manipulations (curettage, endometrial ablation, manual exploration of the postpartum uterine cavity), cesarean section, pelvic inflammatory disease, uterine artery embolization, submucous leiomyoma.

2.2 Physical Examination

• To prevent hemorrhage, bimanual vaginal examination is not recommended [27].

GCR CLOE 5Grade of Recommendation C (Level of Evidence 5)

Comment: There are no data on the safety of bimanual vaginal examination in pregnant women with placenta previa and accreta. If necessary, examine the cervix using specula.

2.3 Laboratory Diagnostics

The evaluation plan should be carried out in accordance with the clinical guidelines "Normal Pregnancy" [1] and "Singleton Labor, Delivery by Cesarean Section" [2].

• All patients are recommended to undergo a complete blood count (CBC) upon admission to the hospital, before surgery, and no later than 72 hours after surgical delivery [28–30].

LeveL of Recommendation BGrade of Evidence 2LeveL of Recommendation B (Grade of Evidence - 2)

Comment: Evaluation and detection of anemia facilitate timely treatment and reduce the risk of negative perinatal outcomes; preoperative anemia reliably increases the rate of maternal complications [28,29].

• All patients are recommended to have their ABO blood group and Rh factor (D antigen), irregular antibodies, and blood group phenotype determined upon hospital admission prior to surgery due to the potential need for blood transfusion in the event of hemorrhage [31,32].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comment: Despite blood typing during pregnancy, all women prior to surgical delivery, in accordance with Order of the Ministry of Health of the Russian Federation No. 183n dated April 2, 2013, "On Approval of the Rules for Clinical Use of Donor Blood and (or) Its Components," must undergo this test in the hospital setting.

Comment: If an infection is detected before scheduled hospitalization, the pregnant woman should be referred to the AIDS Center for confirmation/exclusion of the diagnosis. According to clause 4.3 of the sanitary and epidemiological rules SP 3.1.5.2826-10 "Prevention of HIV Infection," the standard laboratory diagnostic method for HIV infection is the simultaneous detection of HIV-1,2 antibodies and HIV p24 antigen using enzyme-linked immunosorbent assay (ELISA) or chemiluminescence immunoassay (CLIA) diagnostic tests [5]. Evaluation and detection of infection contribute to postnatal prevention of vertical transmission to the newborn [35][6].

Comments: Vertical transmission of hepatitis B can be reduced by administering immunoglobulin and vaccination to the infant.

Comment: In hepatitis C, elective cesarean section is not recommended in the absence of other indications. The risk of transmission is not reduced by operative delivery [8].

Comments: If the test result is positive, antibiotic prophylaxis is prescribed to the patients [9].

[1] RHoOG. Clinical Guidelines "Normal Pregnancy". 2021.

[2] RHoOG. Clinical Guidelines "Single-fetus delivery, delivery by cesarean section"[2]. 2021.

[3] Guidelines for Perinatal Care. 8th Edition. ACOG&AAP, 2017

[4] Order of the Ministry of Health of the Russian Federation No. 1130n dated October 20, 2020, "On Approval of the Procedure for Providing Medical Care in the Profile 'Obstetrics and Gynecology (excluding the use of assisted reproductive technologies)'".

[5] Sanitary and Epidemiological Rules "Prevention of HIV Infection" (Resolution of the Chief State Sanitary Doctor of the RF No. 1 dated January 11, 2011, as amended on July 21, 2016).

[6] CDC. Sexually transmitted diseases treatment guidelines 2002. Morbidity and Mortality Weekly Report  2002;51:1–80.

[7] Order of the Ministry of Health of the Russian Federation No. 1130n dated October 20, 2020, "On Approval of the Procedure for Providing Medical Care in the Profile 'Obstetrics and Gynecology (excluding the use of assisted reproductive technologies)'".

[8] NICE Caesarean section Clinical guideline Published: 23 November 2011Last updated August 2019

[9] RHoOG. Clinical Guidelines "Normal Pregnancy". 2021.

2.4 Instrumental Diagnostics

Ultrasonography.

• During the 1st prenatal screening (11-13⁶ weeks) and 2nd prenatal screening (18-20⁶ weeks), it is recommended to determine ultrasound markers of placenta previa/accreta in all women with a uterine scar and/or clinical risk factors for placenta accreta [5,24,25,27].

GrR ALE 2Level of Recommendations Assurance A (Level of Evidence - 2)

Comment: Placenta accreta following previous operative deliveries occurs as a result of blastocyst implantation into the niche formed after a prior cesarean section. This condition can be diagnosed using ultrasound methods. A prospective study showed that in women at high risk for placenta accreta (previous uterine surgeries and low-lying placenta), the identification of ultrasound signs of placenta accreta at 12–16 weeks of gestation had a high prognostic value [44]. Ultrasound signs of placenta accreta in the first trimester (up to 14 weeks of gestation) include: low implantation of the gestational sac near the scar from the previous cesarean section (sensitivity 44.4%, specificity 67.5%), with additional signs being a decrease in the thickness of the myometrium underlying the gestational sac (less than 5–6 mm) and intraplacental lacunae (sensitivity 33.1%, specificity 93.4%). The combination of all signs is associated with the risk of developing severe grades of placenta accreta (OR 19.6 [95% CI, 6.7 – 57.3]). A myometrial thickness of less than 2 mm on ultrasound at 9–14 weeks of gestation is associated with a high risk of placenta accreta and complications related to this condition.

• If a low-lying placenta (less than 20 mm from the internal os) or placenta previa is detected during ultrasound in the 2nd trimester, a follow-up transvaginal ultrasound is recommended at 32 weeks of gestation to diagnose cases of persistent low-lying placenta or placenta previa [1,25,39,45].

GCR CLEL 4Grade of Recommendation C (Level of Evidence - 4)

Comment: In cases of placenta previa or low-lying placenta at 32 weeks of gestation, it is recommended to repeat the ultrasound at 36 weeks to determine the position of the placental edge and choose the mode of delivery [1,25].

The schedule of antenatal ultrasound monitoring for placenta previa and low-lying placenta in asymptomatic patients is given in Appendix B6 [46].

• In patients with placenta previa or low-lying placenta according to transabdominal ultrasound, it is recommended to perform transvaginal ultrasound to clarify placental localization, assess the placental edge (including thickness, presence of a marginal sinus), detect additional placental lobes, and identify umbilical cord insertion close to the cervix [3].

GCR CLEL 5Grade of Recommendation C (Level of Evidence - 5)

Comment: Cervical length is a predictor of antenatal hemorrhage and emergency preterm cesarean section. In patients with a low-lying placenta, a cervical length < 2 cm was associated with an increased risk of antenatal hemorrhage and preterm delivery. In patients with placenta previa, a cervical length < 3 cm was associated with an increased risk of antenatal hemorrhage and the need for emergency cesarean section.

• In patients with placenta previa or placental location in the area of a uterine scar from a previous cesarean section, it is recommended to perform a targeted search for signs of placenta accreta at each ultrasound examination [8,39,48].

Level of Evidence AGrade of Recommendation 1Level of Recommendation A (Level of Evidence — 1)

Comment: To improve the diagnostic yield of placenta accreta during ultrasound, it is recommended to: use a high-frequency convex transducer (linear, if available) (5–9 MHz); have the pregnant woman's bladder partially filled (approximately 200–300 ml); avoid excessive pressure on the anterior abdominal wall of the pregnant woman with the transabdominal transducer [49].

Comment: in the second trimester of pregnancy, it is possible to diagnose placenta accreta in 90% of cases in patients with placenta previa (provided it is performed by an experienced specialist) [8,25,39,45,50].

• When suspecting or clarifying the diagnosis of placenta accreta, it is recommended to use color Doppler mapping [7,8,25,39].

GCR CLEL 5Grade of Recommendation C (Level of Evidence - 5)

Comment: A standardized description of ultrasound signs of placenta accreta and a sample ultrasound protocol in suspected cases of placenta accreta are presented in Appendices A3.3–A3.4 [1,49,51,52].

Main ultrasound signs of placenta accreta:

• Placental lacunae

• Disappearance of the normal hypoechoic retroplacental clear zone

• Abnormal structure of the uterovesical interface

• Pathological blood flow pattern on color Doppler mapping [49,50,53].

Loss of the hypoechoic retroplacental zone and subplacental hypervascularization are more characteristic of placenta increta, whereas vascular lacunae and a "uterine bulge" are associated with deeper invasion grades (placenta percreta) [8,51].

Ultrasound allows the diagnosis of placenta accreta, but does not provide reliable information to determine the depth of placental invasion. The sensitivity and specificity of ultrasound increase with the severity of placenta accreta [8,39,54]. Ultrasound and MRI have higher specificity and sensitivity in patients with placenta previa and a prior cesarean scar than in patients without this combination of risk factors. Cases with prenatally diagnosed placenta accreta are associated with an increased risk of deep placental invasion and bladder wall injury.

Prenatal diagnosis of placenta accreta reduces the risk of intra- and postoperative hemorrhage, the need for blood component transfusion, and injury to adjacent organs and structures [25,55,56].

• In patients with risk factors and no ultrasound evidence of placenta accreta during the 1st and 2nd prenatal screenings, it is recommended to evaluate ultrasound markers of placenta accreta at 28–30 weeks and 32–34 weeks [57,58].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comment: Intraoperative ultrasound scanning is performed under sterile conditions. The benefit of making the incision away from the placental bed outweighs the theoretical risk of introducing infection into the surgical wound. Therefore, whenever possible, intraoperative uterine ultrasound should be used to determine the upper edge of the placenta and decide on the uterine incision site. In cases of anterior placenta previa, an incision through the placenta is associated with the risk of maternal hemorrhage. Avoiding an incision through the placenta reduces the need for maternal blood component transfusion during or after surgery.

Magnetic Resonance Imaging

Comment: MRI is a more accurate diagnostic method for assessing the depth and topography of invasion, as well as in cases of placental invasion into the posterior uterine wall. The sensitivity of MRI for diagnosing placenta accreta is 94.4%, placenta increta is 100%, and placenta percreta is 86.5%. The specificity of MRI for diagnosing placenta accreta is 98.8%, placenta increta is 97.3%, and placenta percreta is 96.8%. Signs of placenta accreta are presented in Appendix A3.5 [11,39].

• Due to its higher diagnostic value, it is recommended to perform magnetic resonance imaging at 24–32 weeks of gestation [25,55,56].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comment: Before 24 weeks of gestation, MRI results are unreliable. Guidelines for performing MRI are presented in Appendix A3.1.

2.5 Other Procedures

• To confirm placenta accreta, it is recommended to perform pathological anatomical examination of biopsy (surgical) material of the placenta (A08.30.001) [60].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comment: Histological examination of sections reveals expanded areas of absent decidua between the placenta and the myometrium. These may include an area with chorionic villi attached directly to the myometrium or abnormal implantation with a layer of fibrinoid and intermediate trophoblast between the placental villi and the myometrium.

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

Conservative therapy and diet therapy are not indicated.

3.1. Pregnancy management

Comment: In the absence of complaints, clinical manifestations, and with full awareness of all potential complications, women with placenta previa and placenta accreta may be managed in an outpatient setting.

Comment: Risk factors for hemorrhage in placenta previa or low-lying placenta:

• Recurrent episodes of ≥ 3 bloody discharge events;

• Placental edge thickness > 1 cm;

• Presence of a marginal sinus;

• Short cervical canal:

  < 3 cm in placenta previa

  < 2 cm in low-lying placenta

• Previous cesarean section

• Bed rest is not recommended for patients with placenta previa. Routine daily activities and light exercise should be encouraged to improve physical, mental, and emotional well-being [3].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

• In patients with placenta accreta who have undergone a course of fetal RDS prevention with a time interval of more than 14 days from the administered course, a repeat course of fetal RDS prevention is recommended prior to planned delivery up to 36 weeks of gestation [67–69][1].

Level of Evidence CReliability of Evidence 4Level of recommendation C (Reliability of evidence - 4)

• In patients with placenta previa / low-lying placenta presenting with cramping pain, it is recommended to administer tocolytic therapy for 48 hours for the prevention of fetal RDS [1,3].

GCR CLEL 5Grade of Recommendation C (Level of Evidence - 5)

Comment: In one-third of women, antepartum hemorrhage in placenta previa is associated with uterine contractions. If maternal or fetal indications for emergency delivery arise, tocolytics should not be used to prolong pregnancy.

• In cervical incompetence in patients with placenta previa / placenta accreta, placement of cervical sutures is not recommended for prolonging pregnancy and reducing the risk of bleeding [1,39].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comment: correction of the cervix is possible by placing an obstetric pessary, which helps reduce the rate of delivery ≤ 34 weeks [70,71].

Comment: Cystoscopy is indicated in patients with suspected placenta accreta invading the urinary bladder according to ultrasound and/or magnetic resonance imaging [74].

• Placement of ureteral catheters is recommended only in cases of suspected placenta percreta with invasion into the parametrium according to MRI and ultrasound and/or when planned hysterectomy [1,39,75,76].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

3.2. Choice of anesthesia

• As part of premedication, it is recommended to administer antacids (A02A), antiemetics (A04), and antifibrinolytic agents (B02A) in prophylactic doses in accordance with the clinical guidelines "Singleton childbirth, delivery by caesarean section" [2] and "Postpartum hemorrhage" [77,78][3].

Comment: Regional anesthesia is considered safe and is associated with a lower risk of bleeding than general anesthesia during cesarean section in women with placenta previa / placenta accreta.

• Transition to general anesthesia is recommended when indications are present: inefficiency of regional anesthesia, uncontrollable massive blood loss with the development of grade III-IV hemorrhagic shock, long duration of surgery [85].

GCR CLEL 4Grade of Recommendation C (Level of Evidence - 4)

• When performing general anesthesia, it is recommended to follow the clinical guidelines "Postpartum hemorrhage". Indications for prolonged mechanical ventilation are:

1. Cardiac arrest;

2. Apnea or bradypnea;

3. Exhaustion of primary and accessory respiratory muscles;

4. Impaired consciousness due to hypoxia;

6. Prolonged tachycardia of hypoxic origin;

7. Pulmonary edema;

8. Hypoxemia unresponsive to inhaled oxygen administration (PaO2 less than 60 mm Hg, SaO2 less than 90%, PaCO2 greater than 55 mm Hg)

9. Hemoglobin level less than 60 g/L [1,39,86].

GCR CLOE 5Grade of Recommendation C (Level of Evidence 5)

• In the perioperative period during mechanical ventilation, it is recommended to monitor basic vital parameters to the following extent: blood pressure, heart rate, SpO2, thermometry, and capnometry [87][4]

Level of Evidence CReliability of Evidence 4Level of recommendation C (Reliability of evidence - 4)

• During infusion-transfusion therapy, it is recommended to use a volume not exceeding 2 times the estimated blood loss [88].

Level of Evidence CReliability of Evidence 4Level of recommendation C (Reliability of evidence - 4)

Comment: A restrictive strategy should be adhered to during infusion therapy. In the event of postpartum hemorrhage with hemodynamic instability or blood loss exceeding 1000 mL, infusion therapy with warm crystalloid solutions up to 2000 mL should be initiated; if arterial hypotension persists, infusion therapy should be continued with 1500 mL of electrolyte solutions** (B05XA) or human albumin** (B05AA), gelatin** (B05AA06), or hydroxyethyl starch** (B05AA07) up to 30 mL/kg [79]. The recommended ratio of infusion and transfusion therapy to blood loss volume is 1:1 [89]. Exceeding the ratio of blood loss volume to infusion therapy volume leads to severe dilutional coagulopathy and increased bleeding [90]. When calculating the volume of infusion and transfusion therapy, one must remember the necessity of transfusing fresh frozen plasma at 12–15 mL/kg in cases of massive blood loss [5]. When calculating the volume and composition of infusion and transfusion therapy in the event of massive hemorrhage, it is recommended to follow the clinical guidelines "Postpartum Hemorrhage" [6].

• During surgical delivery for placenta accreta, it is recommended to use blood-saving technologies, including intraoperative blood reinfusion to reduce blood loss volume [91–93] (see Appendix B4).

GCR CLOE 5Grade of Recommendation C (Level of Evidence 5)

3.3 Delivery

• Delivery is recommended to be performed by a multidisciplinary team [94–98] [7].

GCR CLEL 4Grade of Recommendation C (Level of Evidence - 4)

Comment: the multidisciplinary team should include: an obstetrician-gynecologist, a functional diagnostics physician and/or radiologist, an anesthesiologist-resuscitologist, a transfusiologist, a surgeon, and a neonatologist. Additionally, a urologist, cardiovascular surgeon, transfusiologist, and a neonatal anesthesiologist-resuscitologist should be readily available for emergency situations. Patients managed by a multidisciplinary team had a lower incidence of hemorrhage, fewer blood transfusions, less coagulopathy and urinary tract trauma, and a shorter duration of hospitalization and intensive care unit stay [96, 97, 99].

Comment: Numerous studies have demonstrated a reduction in blood loss volume during elective delivery compared to emergency delivery [102, 105–107]. To reduce the risk of neonatal morbidity, it is advisable to prolong pregnancy up to 36 + 0 weeks if there have been no multiple minor episodes of vaginal bleeding (>3 episodes), no single episode of significant vaginal bleeding, no premature rupture of membranes, and no history of preterm birth (<36+0 weeks) during the current pregnancy. If the aforementioned factors are present, elective cesarean section is recommended at 34+0 weeks of gestation, given the increased risk of preterm birth [104].

Comment: prolongation of pregnancy up to 36+6 weeks is possible in exceptional cases, provided there is continuous patient monitoring and round-the-clock availability of general and vascular surgeons.

• In women with asymptomatic placenta previa, in the absence of other obstetric or maternal indications, elective delivery at 36+0 – 37+6 weeks via cesarean section is recommended [66].

GCR CLEL 5Grade of Recommendation C (Level of Evidence - 5)

Comment: The risk of hemorrhage, labor, or hemorrhage and labor leading to the need for emergency delivery increases with gestational age, whereas the risks of morbidity associated with prematurity decrease. The risk of hemorrhage is: 4.7% for 35 weeks, 15% for 36 weeks, 30% for 37 weeks, and 59% for 38 weeks of gestation.

• In women with a low-lying placenta where the placental edge is ≤ 20 mm, elective delivery at 37 + 0 – 38 + 6 weeks via cesarean section is recommended [3].

GCR CLEL 5Grade of Recommendation C (Level of Evidence - 5)

Comment: Risk factors for hemorrhage in placenta previa or low-lying placenta:

• Recurrent bleeding episodes ≥3

• Placental edge thickness > 1 cm

• Presence of a marginal sinus

• Short cervical canal (<3 cm in placenta previa, <2 cm in low-lying placenta)

• Previous cesarean section [3].

• In placenta previa or low-lying placenta, elective delivery via cesarean section is recommended [66] [8], [9]

LeR CLoE 5Level of Recommendation C (Level of Evidence — 5)

Comment: This indication is absolute; randomized trials are impossible. Vaginal delivery in cases of partial placenta previa located less than 2 cm from the internal os according to ultrasound is possible in some cases in multiparous women, as well as upon admission to the hospital in the first stage of labor, in the absence of bleeding, provided amniotomy is performed in a fully equipped operating room.

• Before surgical intervention, it is recommended to inform patients with placenta accreta about the high risk of hysterectomy and other complications, and to obtain consent for hysterectomy [17].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comment: In cases of placenta accreta, midline laparotomy is the preferred method [75,110]. In cases of placenta previa or morbidly adherent placenta, a lower transverse laparotomy incision may be used.

Comment: Prophylactic administration of oxytocin and its analogues (H01BB) immediately after delivery promotes uterine contraction, which can be useful for placental separation. However, in cases of incomplete placental invasion, uterine contraction can cause partial placental detachment, leading to increased blood loss, which may prompt the surgeon either to forcibly remove the remaining part of the placenta or to perform a hysterectomy. Uterotonic therapy can be administered using the following drugs: oxytocin** 1 ml (5 IU) intravenously slowly (over 1–2 min) or via an intravenous infusion pump at a rate of 16.2 ml/hour (27 mIU/min), or via an IV drip at a rate of 40 drops/min (5 IU in 500 ml of sodium chloride**); carbetocin** 1 ml (100 mcg) intravenously slowly over 1 minute (only in the presence of risk factors for intra- and postoperative bleeding).

Comment: When performing hysterotomy, incision of the placenta must be avoided; if placenta accreta is clearly identified upon opening the abdominal cavity, a high transverse incision should be made 4–5 cm above the presumed upper edge of the placenta or in the uterine fundus, which will reduce blood loss from the placental bed [110,112].

Comment: performing a transverse incision in the lower uterine segment increases intraoperative blood loss compared to an incision outside the placental site. Performing a fundal cesarean section reduces blood loss and maternal complications [75,110,113].

Comment: There are three surgical tactics for placenta accreta:

• Uterine-sparing surgery

• Hysterectomy

• Leaving the placenta in situ followed by delayed hysterectomy

The primary treatment method for placenta accreta spectrum is hysterectomy. If conditions permit (an experienced surgical team, absence of massive blood loss and invasion of the placenta into the parametrium or cervix), organ-sparing surgery is performed. If placenta accreta is an intraoperative finding, leaving the placenta in situ is recommended until experienced specialists arrive or the patient is evacuated [39,75]. Organ-sparing surgery can reduce blood loss volume, maternal morbidity, and mortality compared to hysterectomy [39,75]. However, organ-sparing management using uterine artery embolization techniques in PAS remains controversial due to the lack of statistically significant studies. Risks of complications reported in the literature include sepsis, thromboembolism, and a recurrence rate of up to 50% in subsequent pregnancies [114,115].

Comment: A retrospective cohort study demonstrated that women managed with organ-sparing techniques experienced lower blood loss volume and a lower rate of complications, including urinary tract injury, secondary hemorrhage, and infections, compared to outcomes in women who underwent hysterectomy [116,117].

• Organ-sparing surgery is not recommended in cases of placental invasion into the cervix and/or parametrium [39,75].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

• In all patients with placenta accreta spectrum, to reduce blood loss volume and improve outcomes, it is recommended to use surgical methods of hemostasis: complex compression hemostasis, ligation/temporary clamping of major vessels, or endovascular techniques [39,110,113,118].

GCR CLEL 4Grade of Recommendation C (Level of Evidence - 4)

Comment: There are several hemostatic methods used in placenta accreta spectrum:

1. Endovascular methods – uterine artery embolization, balloon occlusion of the internal or common iliac arteries, or the aorta;

2. Uterine devascularization – uterine artery ligation, ligation or temporary occlusion of the internal iliac arteries, or temporary occlusion of the common iliac arteries [119].

3. Complex compression hemostasis.

The choice of hemostatic method depends on the surgeon's preference and clinic equipment. The choice of compression suture type depends on the surgeon's experience and preference. Each of the above-listed methods can be used either independently or in combination with others.

To stop hypotonic postpartum hemorrhage and bleeding from the placental site, uterine artery ligation can be combined with a subsequent compression suture [120].

In case of bleeding from the lower uterine segment, two parallel vertical compression sutures can be placed on the anterior and posterior walls of the uterus to rapidly stop bleeding [121].

In case of bleeding from the placental site with a low-lying placenta, a supraplacental gathering suture can be placed [122] (see Appendix B3).

Comment: When comparing prophylactic uterine artery embolization with no embolization, no difference was observed in blood loss, hysterectomy rate, or massive blood transfusion rate. However, one patient in the embolization group developed uterine necrosis requiring hysterectomy [123,124].

Comment: Balloon occlusion of the internal iliac arteries does not contribute to reducing blood loss volume.

• In the absence of life-threatening bleeding and the inability to perform the surgery for placenta accreta spectrum in a single stage (absence of a surgeon, insufficient experience of the obstetrician-gynecologist), it is recommended to leave the placenta in situ [1,39,128].

GDR CLE 5Grade of recommendation C (level of evidence – 5)

Comment: After leaving the placenta in situ, the patient must be admitted to the intensive care unit under the dynamic supervision of an obstetrician-gynecologist and an anesthesiologist [1,7]. There is no evidence of benefit from planned delayed hysterectomy [75,129]. The "placenta in situ" approach, or expectant management, consists of leaving the entire placenta untouched and waiting for its complete resorption, the arrival of a qualified surgical team, or the patient's evacuation. Attempting forcible removal of the placenta significantly increases blood loss, hysterectomy rates, infection, and disseminated intravascular coagulation: a 40% risk of subsequent emergency hysterectomy with a 42% probability of maternal mortality is indicated [128,130].

Endovascular methods.

Comment: Occlusion of the common iliac arteries is associated with a reduced risk of massive intraoperative blood loss. The method is safe and effective in patients with placenta accreta spectrum. Prophylactic balloon occlusion of the abdominal aorta is the most effective endovascular intervention method. Aortic balloon occlusion should be performed below the renal arteries; this leads to less blood loss and reduces the risk of postpartum hemorrhage from the ovarian arteries.

• As an intraoperative hemostatic method to perform metroplasty in placenta accreta spectrum, it is recommended to use complex compression hemostasis [113,135].

GCR CLEL 4Grade of Recommendation C (Level of Evidence - 4)

Comment: The technique of complex compression hemostasis is described above. It has been shown that the use of a Foley catheter as a tourniquet for hemostasis reduced blood loss volume and the hysterectomy rate [135].

• If other methods of surgical hemostasis are ineffective, it is recommended to place compression uterine sutures (B-Lynch suture) for hypotonic hemorrhage [12,16,120].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

Comment: Compression uterine sutures (B-Lynch suture) are effective for hypotonic hemorrhage [120].

3.4 Prevention of postpartum hemorrhage

Comment: The use of an intrauterine balloon is associated with a reduced risk of postpartum hemorrhage due to uterine atony in placenta previa and accreta.

3.5 Management of puerperas after cesarean section

In patients with placenta previa/accreta, it is recommended to follow the management plan according to the guidelines "Singleton delivery, delivery via Cesarean section" [11]

Comment: Preserving fertility in patients with placenta accreta spectrum is possible. With successful conservative treatment, the subsequent pregnancy rate ranges from 86% to 89%. Women should be warned that the risk of recurrent placenta accreta ranges from 22% to 29%.

[1] NICE. Preterm labour and birth. Clinical Guideline [NG25] 2015

[2] RUSOG. Clinical guidelines "Single-term pregnancies, delivery by Cesarean section". 2021

[3] RUSOG. Clinical guidelines "Postpartum hemorrhage". 2021

[4] RCOG. Prevention and Management of Postpartum Haemorrhage. Green‐top Guideline No. 52. December 2016

[5] RCOG. Prevention and Management of Postpartum Haemorrhage. Green‐top Guideline No. 52. December 2016

[6] RUSOG. Clinical guidelines "Postpartum hemorrhage"

[7] FIGO. Consensus guidelines on placenta accreta spectrum disorders: Prenatal diagnosis and screening

[8] American College of Obstetricians and Gynecologists. ACOG committee opinion no. 764: Medically indicated Late-Preterm and Early-Term Deliveries. Obstet Gynecol. 2019

[9] American College of Obstetricians and Gynecologists. ACOG committee opinion. Placenta accreta. Number 266, January 2002. Committee on Obstetric Practice Int J Gynaecol Obstet. 2002;77(1):77.

[10] Methodological Letter of the Ministry of Health and Social Development of the RF dated May 6, 2014 N 15-4/10/2-3190 "Cesarean section. Indications, anesthesia methods, surgical technique, antibiotic prophylaxis, postoperative management"

[11] Russian Society of Obstetricians and Gynecologists (ROAG). Clinical guidelines "Singleton delivery, delivery via Cesarean section" .

4. Medical Rehabilitation and Sanatorium-Resort Treatment

Not applicable.

5. Prevention and Dispensary Observation

• In patients with placenta previa/accreta, it is recommended to adhere to the prevention and dispensary monitoring plan according to the clinical guidelines "Single-term pregnancies, delivery by Cesarean section"[139].

GCR CLEL 4Grade of Recommendation C (Level of Evidence - 4)

6. Organization of Medical Care

• Delivery in patients with placenta accreta/previa is recommended to be planned in a Level 3 hospital [39,75].

LoR CGoE 5Level of Recommendation C (Grade of Evidence - 5)

7. Additional Information

Not applicable.

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

1. Roman G. Shmakov – MD, PhD, Professor, Professor of the Russian Academy of Sciences, Director of the Institute of Obstetrics, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow), Chief Freelance Specialist in Obstetrics of the Russian Ministry of Health. There is no conflict of interest.

2. Mark A. Kurtser – MD, PhD, Professor, Academician of the Russian Academy of Sciences, Head of the Department of Obstetrics and Gynecology, Pediatric Faculty, Pirogov Russian National Research Medical University of the Russian Ministry of Health (Moscow). There is no conflict of interest.

3. Sergey V. Barinov – MD, PhD, Professor, Head of the Department of Obstetrics and Gynecology No. 2, Omsk State Medical University of the Ministry of Health of the Russian Federation, freelance expert of the territorial administration of Roszdravnadzor for the Omsk Region (Omsk). There is no conflict of interest.

4. Natalia V. Artymuk – MD, PhD, Professor, Head of the Department of Obstetrics and Gynecology named after Prof. G.A. Ushakova, Kemerovo State Medical University of the Ministry of Health of the Russian Federation, President of the Kemerovo Regional Public Organization "Association of Obstetricians and Gynecologists", Chief Freelance Specialist of the Ministry of Health of the Russian Federation in Obstetrics and Gynecology in the Siberian Federal District, Member of the Presidium of the Association of Obstetric Anesthesiologists-Resuscitators (Kemerovo). There is no conflict of interest.

5. Elrad Yu. Amiraslanov – MD, PhD, Head of the Obstetric Department, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). There is no conflict of interest.

6. Bashmakova Nadezhda Vasilievna – MD, PhD, Professor, Chief Researcher, Ural Research Institute of Maternal and Infant Care of the Russian Ministry of Health, Chief Freelance Specialist of the Russian Ministry of Health in Obstetrics and Gynecology in the Ural Federal District (Yekaterinburg). No conflict of interest.

7. Tatyana E. Belokrinitskaya – MD, PhD, Professor, Honored Doctor of the Russian Federation, Head of the Department of Obstetrics and Gynecology of the Faculty of Advanced Training and Professional Retraining of Specialists, Chita State Medical Academy of the Ministry of Health of the Russian Federation, Chief Freelance Specialist of the Ministry of Health of the Russian Federation in Obstetrics and Gynecology in the Far Eastern Federal District, Member of the Board of the Russian Society of Obstetricians and Gynecologists, Member of the Presidium of the Association of Obstetric Anesthesiologists-Resuscitators, Deputy of the Legislative Assembly of the Zabaykalsky Krai, President of the Trans-Baikal Society of Obstetricians and Gynecologists (Chita). There is no conflict of interest.

8. Vladimir G. Bychenko – MD, PhD, Member of the European Society of Radiology (ECR), Head of the Department of Diagnostic Radiology, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). There is no conflict of interest.

9. Oksana N. Vasilchenko – MD, PhD, physician of the 2nd Maternity Ward, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). There is no conflict of interest.

10. Ashot M. Grigoryan – MD, PhD, Head of the Department of X-ray Endovascular Diagnostics and Treatment, Lapino Clinical Hospital, Mother and Child Group of Companies. There is no conflict of interest.

11. Kirill A. Desyatnik – Obstetrician-gynecologist, Organizational and Methodological Department, Yekaterinburg Clinical Perinatal Center. There is no conflict of interest.

12. Tatyana M. Zabelina – Physician of the 2nd Maternity Ward, Postgraduate student, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). There is no conflict of interest.

13. Oleg V. Ionov – MD, PhD, Head of the Prof. A.G. Antonov Intensive Care Unit, Institute of Neonatology and Pediatrics, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health, Associate Professor at the Department of Neonatology, Pediatric Faculty, I.M. Sechenov First Moscow State Medical University of the Russian Ministry of Health (Sechenov University) (Moscow). There is no conflict of interest.

14. Tamara E. Karapetyan – MD, PhD, Obstetrician, Obstetric Department, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). There is no conflict of interest.

15. Aleksey Yu. Korolev – Anesthesiologist-resuscitator, Department of Anesthesiology and Intensive Care, Assistant at the Department of Anesthesiology and Intensive Care, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). There is no conflict of interest.

16. Sergey V. Martirosyan – MD, PhD, Chief Medical Officer, Yekaterinburg Clinical Perinatal Center, Associate Professor at the Department of Obstetrics and Gynecology, Faculty of Medicine and Prophylaxis, Ural State Medical University. There is no conflict of interest.

17. Alexandra A. Mikheeva – Postgraduate student, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). There is no conflict of interest.

18. Anna A. Olina – MD, PhD, Professor, Deputy Director of the Department of Medical Care for Children and Obstetrics Services, Ministry of Health of the Russian Federation.

19. Olga V. Perevozkina – MD, PhD, Head of the Organizational and Methodological Department, Yekaterinburg Clinical Perinatal Center. There is no conflict of interest.

20. Andrey M. Prikhodko – MD, PhD, Physician of the 1st Maternity Ward, Assistant at the Department of Obstetrics and Gynecology, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). There is no conflict of interest.

21. Aleksey V. Pyregov – MD, PhD, Professor, Director of the Institute of Anesthesiology, Reanimatology and Transfusiology, Head of the Department of Anesthesiology and Intensive Care, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after V.I. Kulakov of the Russian Ministry of Health. Chairman of the Committee on Anesthesiology and Intensive Care in Obstetrics and Gynecology of the Association of Anesthesiologists-Resuscitators (Moscow). There is no conflict of interest.

22. Rogachevsky Oleg Vladimirovich — Doctor of Medical Sciences, Professor at the Department of Anesthesiology and Critical Care Medicine, Head of the Department of Extracorporeal Detoxification Methods and Quantum Hemotherapy, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). No conflict of interest.

23. Savelyeva Galina Mikhailovna — Academician of the Russian Academy of Sciences, Doctor of Medical Sciences, Professor, Honored Scientist of the Russian Federation, Professor at the Department of Obstetrics and Gynecology, Pediatric Faculty, Pirogov Russian National Research Medical University (Moscow). No conflict of interest.

24. Strelnikova Elena Vladimirovna — Candidate of Medical Sciences, Physician at the Department of Extracorporeal Detoxification Methods and Quantum Hemotherapy, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). No conflict of interest.

25. Troshin Pavel Vladimirovich — Anesthesiologist-Intensivist at the Department of Anesthesiology and Critical Care Medicine, Assistant at the Department of Anesthesiology and Critical Care Medicine, National Medical Research Center for Obstetrics, Gynaecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). No conflict of interest.

26. Fatkullin Farid Ildarovich — Candidate of Medical Sciences, Head of the RD Department, City Clinical Hospital No. 7 of Kazan, Associate Professor at the V.S. Gruzdev Department of Obstetrics and Gynecology, Kazan State Medical University of the Russian Ministry of Health. No conflict of interest.

27. Fedorova Tatyana Anatolyevna — Doctor of Medical Sciences, Professor, Deputy Director of the Institute of Anesthesiology, Critical Care Medicine and Transfusiology, Head of the Department of Transfusiology and Extracorporeal Hemocorrection, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). President of the National Association of Patient Blood Management Specialists. No conflict of interest.

28. Yarygina Tamara Alexandrovna — Candidate of Medical Sciences, Ultrasound Diagnostics Physician, National Medical Research Center for Obstetrics, Gynecology and Perinatology named after Academician V.I. Kulakov of the Russian Ministry of Health (Moscow). No conflict of interest.

Appendix A2. Methodology for Developing Clinical Guidelines

Target audience for these clinical guidelines:

1. obstetrician-gynecologists

2. obstetrics and gynecology residents

Table 1. Level of Evidence (LoE) grading scale for diagnostic methods (diagnostic interventions)

Table 2. Level of Evidence (LoE) grading scale for prevention, treatment, and rehabilitation methods (preventive, therapeutic, and rehabilitative interventions)

Table 3. Grade of Recommendation (GoR) scale for prevention, diagnostic, treatment, and rehabilitation methods (preventive, diagnostic, therapeutic, and rehabilitative interventions)

Appendix A3. Reference Materials

Related documents:

• Order of the Ministry of Health of the Russian Federation No. 1130n dated October 20, 2020, "On Approval of the Procedure for Providing Medical Care in the Field of Obstetrics and Gynecology". Federal Law No. 61-FZ of April 12, 2010 (as amended on July 3, 2016) "On the Circulation of Medicines".

• Postpartum Hemorrhage (2018) [Letter of the Ministry of Health of the Russian Federation No. 15-4/i/2-2535 dated March 26, 2019].

• RUOG. Clinical Guidelines "Normal Pregnancy". 2021.

• RUOG. Clinical Guidelines "Venous Complications During Pregnancy and the Postpartum Period. Obstetric Embolism". 2021.

• RUOG. Clinical Guidelines "Singleton Delivery, Spontaneous Delivery in Occipital Presentation (Normal Labor)". 2021.

• RUOG. Clinical Guidelines "Singleton Delivery, Delivery by Cesarean Section". 2021.

• Decree of the Government of the Russian Federation No. 897 of June 22, 2019, "On Approval of the Rules for Procurement, Storage, Transportation, and Clinical Use of Donor Blood and Its Components and on Invalidation of Certain Acts of the Government of the Russian Federation".

• Order of the Ministry of Health of the Russian Federation No. 919n of November 15, 2012, "On Approval of the Procedure for Providing Medical Care to Adult Patients in the Field of Anesthesiology and Critical Care Medicine".

• Order of the Ministry of Health of the Russian Federation No. 1170n of October 28, 2020, "On Approval of the Procedure for Providing Medical Care to the Population in the Field of Transfusiology".

• Letter of the Chief Non-Staff Anesthesiologist-Intensivist of the Ministry of Health of the Russian Federation dated December 29, 2016, No. 102/OD-MZ/2016

• Order of the Ministry of Health of the Russian Federation No. 919n of November 15, 2012, "On Approval of the Procedure for Providing Medical Care to Adult Patients in the Profile 'Anesthesiology and Intensive Care'."

• Collection of the Federal Research Institute for Health Organization and Informatics of the Russian Ministry of Health, "Main indicators of maternal and child health, the activities of the child and maternity welfare services in the Russian Federation", Moscow, 2019.

• Methodological Letter of the Ministry of Health and Social Development of the Russian Federation No. 15-4/10/2-3190 of May 6, 2014, "Cesarean Section: Indications, Anesthesia Methods, Surgical Technique, Antibiotic Prophylaxis, Postoperative Management".

• WHO Surgical Safety Checklist Implementation Manual, 2009.

• Evidence-based clinical guidelines 'Physical and Rehabilitation Medicine' by G.N. Ponomarenko, D.V. Kovlen, Saint Petersburg, 2018.

Appendix A3.1 Guidelines for MRI scanning

• It is recommended to perform the examination on 1.5T or 3T magnetic field strength scanners using surface coil(s).

• Intravenous administration of paramagnetic contrast agents is not recommended.

• It is recommended to perform scanning using single-shot 2D T2-weighted (SSFSE/HASTE/UFSE) pulse sequences, obtaining images in transverse (axial), coronal, and sagittal planes, as well as obtaining images in an oblique transverse (axial) plane perpendicular to the myometrium-placenta complex.

• Recommended slice thickness is less than 4 mm. The use of T2-weighted pulse sequences with fat suppression is not recommended.

• It is recommended to perform multiplanar steady-state free precession (SSFP) pulse sequences to determine the vascular pattern and placental boundaries.

• Diffusion-weighted imaging (DWI) pulse sequences are recommended to determine placental boundaries in patients with severely altered myometrium, although there is a lack of literature evaluation for DWI in this pathology.

• The examination is performed with the patient in the supine position with a moderately filled bladder [59].

Appendix A3.2 Clinical evaluation of the degree of placenta accreta [25].

Appendix A3.3 Unified ultrasound signs of placenta accreta spectrum [52-54].

Appendix A3.4 Sample ultrasound report template for suspected placenta accreta spectrum

Appendix A3.5 Signs of placenta accreta on MRI

Heterogeneous placental intensity, asymmetrical shape/thickness of the placenta, placental infarctions, and areas of abnormal vascular pattern in the placenta are not significant for making the diagnosis.

Appendix B. Physician Action Algorithms

Appendix B1. Surgical safety algorithm for placenta accreta spectrum (in the operating room).

Appendix B2. Algorithm for inpatient physicians

1. Diagnosis of placenta previa by ultrasound, placenta accreta spectrum disorders by ultrasound and MRI.

2. Choice of skin incision:

lower midline laparotomy (in patients with placenta accreta spectrum)

transverse suprapubic laparotomy (in patients with placenta previa)

3. Choice of uterine incision: fundal cesarean section (in patients with placenta accreta spectrum)

lower uterine segment cesarean section (in patients with placenta previa)

4. Choice of surgical management for placenta accreta spectrum

organ-preserving (in focal placenta accreta spectrum)

- metroplasty using comprehensive compression hemostasis and/or endovascular hemostatic methods and/or ligation, temporary occlusion of main uterine vessels, hemostatic sutures.

- hysterectomy (when placenta accreta involves the cervix, when bleeding cannot be controlled)

- leaving the placenta in situ (placenta accreta as an intraoperative finding)

Appendix B3. Methods of distal compression hemostasis

In obstetric practice during delivery in pregnant women with abnormal placentation, 2 methods of distal compression hemostasis are used:

1. Comprehensive compression hemostasis, including the application of tourniquets[113];

2. Combined approach using uterine and vaginal catheters[140].

I. Technique of partial resection using comprehensive compression hemostasis.

1. Fundal cesarean section, fetal extraction, umbilical cord ligation without traction, placing it into the uterine cavity, and closure of the uterus with a double-layer suture.

2. Comprehensive compression hemostasis

Dissection of the peritoneum and vesicouterine fold is performed, followed by bladder mobilization with targeted vessel coagulation, creation of artificial windows in the broad ligaments of the uterus, and placement of tourniquets bilaterally and onto the cervico-isthmic region through these windows. The ovaries are displaced laterally to the tourniquets, creating a loop from the tourniquet that includes the fallopian tube, mesosalpinx, and proper ovarian ligament. As a result, the tubal and communicating branches of the ovarian and uterine arteries are clamped[141].

3. Metroplasty - excision of the anterior uterine wall segment with the invasive placenta followed by metroplasty using controlled intrauterine balloon tamponade [113].

Filling the urinary bladder with methylene blue facilitates visualization of the surgical field [39].

II. Technique of the combined approach using Zhukovsky uterine and vaginal catheters.

In placenta previa.

1. After urinary bladder catheterization prior to surgical delivery, a Zhukovsky vaginal catheter was inserted (without filling it with fluid), a high transverse incision was made on the uterus, and immediately following fetal extraction, the vaginal catheter was filled with 180 ml of normal saline.

2. Further surgery is performed with the vaginal catheter filled. Immediately after fetal extraction, ligation of the descending branch of the uterine artery is performed. The next step, following placental delivery, is inspection of the placental bed and ligation of bleeding vessels. Separation of the vesicouterine fold downwards and placement of a hemostatic extrauterine supraplacental purse-string suture. Insertion of the intrauterine catheter using an introducer through the hysterotomy incision, guiding it with the surgeon's index finger through the cervical canal into the axial tube of the vaginal catheter. Restoration of the uterine wall with interrupted Vicryl sutures. The duration of balloon tamponade using the vaginal and uterine catheters is 10–14 hours.

In placenta accreta.

1. If placenta accreta involving 1/3 of the myometrial thickness is detected, excision of the affected area is performed with simultaneous ligation of bleeding vessels and figure-of-eight suturing of the placental bed. Subsequently, the vesicouterine fold is separated downwards, and a hemostatic extrauterine supraplacental purse-string suture is placed.

2. If placenta accreta involving more than 2/3 of the myometrial thickness is detected, or if the affected area is greater than 5 centimeters in diameter, the portion of the uterus with the invaded placenta is excised. Separation of the vesicouterine fold and placement of a hemostatic extrauterine supraplacental purse-string suture below the intended uterine wall resection line. Subsequently, the angles of the uterine wall are repaired, the intrauterine catheter is inserted, the uterine wall is then repaired, and the uterine catheter is filled with normal saline.

3. In the case of a placental hernia, a high transverse incision is made on the uterus to extract the fetus, followed by metroplasty: isolation of the hernia sac, separation of the vesicouterine fold, hemostasis of paravesical vessels, and placement of a hemostatic extrauterine supraplacental purse-string suture below the intended uterine wall resection line. Insertion of the intrauterine catheter using an introducer through the hysterotomy incision, guiding it with the surgeon's index finger through the cervical canal into the axial tube of the vaginal catheter. Subsequently, the uterine wall is also repaired using interrupted Vicryl sutures. The duration of balloon tamponade using the vaginal and uterine catheters is 10–14 hours [140].

Appendix B4. Intraoperative autologous red blood cell salvage technology.

For intraoperative autologous red blood cell reinfusion (IAR), Cell Saver or Cats autotransfusion devices and disposable administration sets are used.

Contraindications to intraoperative autologous red blood cell salvage in obstetrics.

Absolute

-presence of purulent contents in the abdominal cavity;

-presence of intestinal contents in the abdominal cavity;

-presence in the shed blood of substances contraindicated for intravascular administration: hydrogen peroxide** (D08AX01), distilled water, collagen-based hemostatic agents (B02), etc.).

Methodology: The principle of the procedure involves aspirating shed blood from the surgical wound, processing it in the device, and subsequently reinfusing the resulting autologous red blood cell suspension (Hct 60%) back into the patient's vascular bed.

Priming of disposable blood tubing sets is performed in the operating room before the start of the surgery. The sterile suction tubing is handed to the scrub nurse.

Collection of blood shed into the operative field is performed by the second assistant. The negative pressure generated by the vacuum aspirator must not exceed 100 mmHg.

Blood aspirated from the surgical field is mixed with a solution of antithrombotic agents (B01A), passes through a filter that traps tissue particles and blood clots, and collects in a reservoir. When the volume of collected blood becomes adequate for the reservoir volume, the first phase of the device's operation begins: filling the processing bowl (centrifuge bowl).

This phase consists of several steps:

1. Acceleration of the centrifuge to 5600 rpm;

2. Transfer of blood from the reservoir to the wash bowl using a peristaltic pump, initiation of the centrifugation process;

3. Filling of the wash bowl continues until red blood cells fill the entire volume of the bowl (the bowl volume may be 125 ml, 175 ml, 225 ml). Plasma separated during centrifugation is discarded along with the anticoagulant into an appropriate waste container. After this, the second phase begins automatically or manually - washing the red blood cells with sterile normal saline.

Washing continues until the specified volume of washing solution (1000–1500 ml in obstetrics) has completely passed through the red blood cells. Centrifugation is maintained throughout this process.

The final phase of the device's operation is emptying the bowl:

1. The centrifuge stops, and the peristaltic pump starts rotating in the reverse direction;

2. Washed autologous red blood cells are pumped from the wash bowl into the reinfusion bag;

Then the process is repeated until all blood aspirated from the wound has been processed. The duration of the first described cycle is 3-5 minutes.

During operation, the device display clearly shows all required parameters: centrifuge speed, pump speed, and volume of processed solution. After each operating cycle, the volume of collected and washed red blood cells is displayed.

Autologous red blood cell reinfusion must be performed using a leucocyte filter within a maximum of 6 hours after obtaining the autologous red blood cells.

Autologous red blood cell reinfusion is an effective method for restoring globular volume in hemorrhages occurring during cesarean section. IAR is recommended for women with an anticipated intraoperative blood loss exceeding 20% of total blood volume (TBV).

Autologous blood salvage should be performed only by qualified personnel who perform it regularly and possess the necessary knowledge and experience. The patient's consent for autologous blood salvage must be obtained. The use of autologous blood salvage in obstetric hospitals must be subject to audit and monitoring. The limitations of the method are mainly associated with the availability of appropriate personnel and equipment.

The use of IAR minimizes the use of donor blood components in hemorrhages of any volume and avoids massive blood transfusion syndrome, while significantly improving the postoperative course and shortening hospital stay.

Appendix B5. Technique of temporary balloon occlusion of the common iliac arteries and the infrarenal abdominal aorta.

The procedure is performed in a conventional surgical operating room using a mobile C-arm fluoroscopy system (hereinafter referred to as C-arm). In the absence of a C-arm, performing the delivery in an endovascular suite can be considered.

Preparation for surgical delivery is standard, including a 4-hour fasting period and no cleansing enema.

Steps:

1. Catheterization of two peripheral veins (14G or 16G catheters) or placement of a central venous catheter (access to the right internal jugular vein is recommended, under ultrasound guidance, using 2- or 3-lumen catheters).

2. Premedication - intravenous administration of atropine**, #famotidine**. For intravenous administration, the single dose is 20 mg, the interval between administrations is 12 hours (instructions) 20 mg #dexamethasone** 8 mg[142,143].

3. Spinal-epidural anesthesia in the lumbar spine is recommended. For subarachnoid administration, hyperbaric bupivacaine** (10–15 mg) is recommended. To maintain anesthesia, epidural anesthesia with ropivacaine** solution at a concentration of 0.2%–0.75% (40–150 mg) can be used.

4. For the prevention and treatment of hypotension, intravenous infusion of balanced crystalloids, administration of adrenergic and dopaminergic agents, and left uterine displacement are performed.

5. Once a sensory block up to the Th4 level is achieved (developed), preparation for the endovascular stage may be considered.

6. Using the Seldinger technique, puncture of the common femoral artery is performed sequentially on both sides.

7. Placement of introducers matching the profile of the balloon catheters intended for use.

8. Fixation of the introducers to the thigh skin.

9. IMPORTANT! Insertion and placement of balloon catheters must be performed only after delivery of the fetus!

10. After delivery of the fetus and closure of the incision in the uterine fundus, the endovascular stage begins.

11. Under fluoroscopic guidance, peripheral balloon catheters are sequentially advanced and placed along diagnostic guidewires into the bifurcation of the abdominal aorta so that their distal tips touch each other, resembling an inverted letter V [80, 118].

12. The diameter of the balloon catheter is selected so that when inflated, it ensures complete cessation of blood flow through the common iliac artery.

13. Balloon catheters are inflated using an inflator (pressure syringe) with a 1:1 mixture of normal saline and contrast agent.

14. After complete inflation of both balloon catheters, the guidewire is removed from the side port of one of them, and a contrast agent is injected.

15. With appropriate selection of the balloon catheters and their complete inflation, contrast stasis is observed above the level of balloon placement in the infrarenal aorta, with no antegrade flow.

16. After angiography, a diagnostic guidewire is reintroduced through the side port of the balloon to stabilize the catheter.

17. If the balloon is positioned correctly and repositioning is not required, it should be fixed to the introducer to prevent migration during the surgical procedure.

18. Peripheral balloon catheters require inflation pressures of up to 8–10 atm to expand, which may be accompanied by vascular wall injury. To prevent this complication, it is advisable to use balloon catheters intended for Rashkind procedures, which expand to a diameter of 13.5 mm without pressure, simply by injecting 2.0 ml of a 1:1 normal saline and contrast agent mixture.

19. After placement of the first balloon described in the previous step, a Cobra-type diagnostic catheter is inserted from the contralateral side to perform angiography. Contrast stasis above the balloon placement zone indicates reliable occlusion of arterial blood flow.

20. After placement of the second balloon, due to its low profile, obtaining adequate angiography to assess reliable blood flow occlusion is not feasible. This can be assessed by changes in the pulse oximetry waveform determined via a sensor pre-placed on the big toe. The absence of a pulse waveform and saturation reading indicates adequate balloon inflation and blood flow occlusion.

21. In the inflated state, any of the used balloon catheters may remain for no more than 10 minutes to prevent lower extremity ischemia. If the surgical procedure for placental extraction requires more time, after 10 minutes, upon agreement with the team, the balloon catheters should be successively deflated for at least 1 minute to restore blood flow in the lower extremity arteries, followed by re-inflation of the balloon catheters [144].

Appendix B6. Scheme of antenatal ultrasound monitoring for placenta previa and low-lying placenta in asymptomatic patients.

Appendix C. Patient Information

Placental accreta is a pregnancy complication in which the placenta is firmly attached to the uterine wall or grows into it.

Normally, at the end of labor, the placenta separates from the uterine wall and is delivered (the so-called delivery of the afterbirth). In abnormal placental attachment, excessive fixation to the uterine wall disrupts placental separation, leads to its retention in the uterine cavity, and causes complications, the most dangerous of which are postpartum hemorrhage and hysterectomy.

Placenta previa is a pregnancy complication in which the placenta is located low relative to the internal os, which may result in bleeding both during pregnancy and in labor.

Placenta accreta and placenta previa are absolute indications for surgical delivery by cesarean section. Cesarean section for placenta accreta is performed at 34–36 weeks of pregnancy, and for placenta previa, at 37–39 weeks of pregnancy. You will be hospitalized in advance at a Level 3 obstetrical hospital for delivery. If labor begins, membranes rupture before the estimated delivery date, or bleeding occurs, you must urgently call an ambulance for hospitalization at an obstetrical hospital. At the hospital, you will undergo the necessary list of laboratory and instrumental examinations depending on the obstetrical situation. For planned hospitalization, you must refrain from eating for 8 hours and from clear liquids for 2 hours before the planned delivery. Clear liquids include water, pulp-free fruit juice, carbonated drinks, tea, and coffee.

Before surgery, you will be consulted by an obstetrician-gynecologist and an anesthesiologist-reanimatologist. You must inform the doctors about all known health and hereditary problems, allergic reactions, individual intolerance to medications and food products, as well as current and past tobacco smoking, alcohol abuse, or drug use. The anesthesiologist-reanimatologist will choose the most appropriate type of anesthesia for you during the surgery. Before surgery, you must wear compression stockings on your legs to prevent thromboembolic complications, which you will wear throughout the entire postoperative period. You must remove hair from the area of the intended incision (perineum, pubic area, lower abdomen). Also, before surgery, you will receive antibiotic prophylaxis to reduce the risk of purulent-inflammatory postoperative complications. If necessary, additional diagnostic methods may be performed before surgery, such as cystoscopy or bladder stenting. To reduce blood loss, endovascular methods of hemostasis may be performed before surgery.

Since placenta accreta is associated with the risk of hysterectomy, before surgery you will sign a consent form for hysterectomy if the uterus cannot be preserved.

In the operating room, an intravenous catheter and a urinary catheter will be placed for the duration of the surgery and the first hours thereafter. During the surgical procedure, if necessary, an ultrasound examination may be performed to refine surgical tactics.

You should be aware that various complications may arise during surgery, which may require additional interventions (vessel ligation, leaving the placenta in situ, repair of bladder or ureter defects), transfusion of donor blood and its components (plasma, red blood cell mass, platelet-leukocyte mass), as well as other protein-containing products. After reading this, you must sign a consent form for these procedures. During surgery, to reduce the risk of postpartum hemorrhage, an intrauterine balloon will be placed, which will be removed 6 hours after the end of surgery.

In the postoperative period, you will be transferred to the intensive care unit for as long as necessary depending on your condition. In the postoperative period, pain management will be continued, and early mobilization will be offered to reduce the risk of postoperative complications: early sitting up in bed and getting up, usually on the 1st postpartum day. Intake of clear liquids is possible immediately after delivery, and eating food is possible a few hours after delivery.

Suture removal is performed in the hospital or after discharge if necessary, as absorbable suture material is used in a number of cases.

After discharge from the hospital, you must follow a prescribed regimen and activity restrictions during the first months: limitation of lifting heavy objects (>5 kg), abstaining from sexual intercourse, and upon its resumption – the use of contraceptive methods recommended by your attending obstetrician-gynecologist, restriction of physical activity. You must visit your attending obstetrician-gynecologist 1–1.5 months after delivery. Planning the next pregnancy, given your uterine scar, is recommended no earlier than 1 year after delivery following a control ultrasound evaluating the condition of the scar.

You should know that a cesarean section is a relatively safe procedure, but complications are possible during the procedure and in the postoperative period:

• Very common - repeat cesarean section in subsequent deliveries (1 case in every 4 surgeries).

• Common - surgical wound pain and abdominal discomfort in the first few months after surgery (9 cases in every 100 surgeries).

• Common - readmission, postpartum infection (5–6 cases in every 100 surgeries).

• Common – fetal injuries, for example, skin laceration by a scalpel (2 cases per 100 surgeries).

• Uncommon - re-operation in the postoperative period, admission to the intensive care unit (5–9 cases in every 1,000 surgeries).

• Uncommon - uterine rupture in a subsequent pregnancy/delivery, placenta previa and accreta, hemorrhage (1–8 cases in every 1,000 surgeries).

• Rare - thrombotic complications, bladder injuries, ureteral injury during surgery (1–5 cases in every 1,000 surgeries).

• Very rare - death (1 woman per 12,000 surgeries).

You should also be aware that the presence of a uterine scar may subsequently reduce your fertility (the ability to conceive and bear children). You should also know that after surgical delivery, a decrease in lactation is noted more frequently than after vaginal delivery.

Surgical Consent Form:

The recommended surgical consent form for placenta previa/accreta should include the following items:

- description of risks associated with placenta accreta (massive blood loss, need for blood component transfusion, injury to the bladder, ureters, adjacent organs and structures, hysterectomy),

- purulent-septic and thromboembolic complications

- consent for additional interventions in case of massive blood loss (embolization, vessel ligation, leaving the placenta in situ, hysterectomy) and other complications (repair of bladder or ureter defects), blood and blood component transfusion.