Classification and pathogenesis of morbidly adherent placenta
Normally, during labor, placental separation occurs at the level of the spongy layer of the decidua. The pathology develops due to alterations in the uterine mucosa or specific features of the chorion.
According to the affected area, the following are distinguished:
- Total: invasion involves the entire placental surface.
- Focal (partial): only a specific area is affected.
Depending on the depth of penetration of the chorionic villurs, the following are distinguished:
- Placenta accreta — villi reach the muscular layer but do not penetrate into it.
- Placenta increta — villi invade directly into the myometrium.
- Placenta percreta (true placenta percreta) — villi penetrate through the entire uterine wall to the serosa.
An additional factor is the increased proteolytic activity of the chorionic villi.
Risk factors for the development of the condition
Disorders of trophoblast formation and endometrial changes occur under the influence of several factors:
- Inflammatory diseases of the endometrium, including specific infections (chlamydia, gonorrhea, tuberculosis) and chronic endometritis.
- Trauma to the mucous membrane due to excessive past uterine curettage.
- Scars on the uterus following a previous cesarean section or myomectomy.
- Bad habits: smoking and drug use.
Instrumental diagnostics
Early detection of the pathology during pregnancy is carried out using modern imaging techniques.
Ultrasound examination:
- 2D mode (standard echogram).
- Color Doppler mapping (CDM) to assess vascularization.
- HDliveflow mode for detailed analysis of the vascular network.
Signs on ultrasound and MRI:
- Absence of the hypoechoic retroplacental zone.
- Large placental vascular lacunae and hypervascularization of the lower segment.
- Thinning, defect, or complete absence of the myometrium, as well as a blurred border between the uterus and the urinary bladder.
- Formation of a "uterine aneurysm" and tortuous vessels extending beyond the organ contour on MRI.
During labor, the diagnosis is confirmed clinically upon attempting manual removal of the placenta.
Management strategy and preoperative preparation
Patients with suspected placenta accreta require strict adherence to routing and preparation protocols:
- Routing: Referral to a Level III obstetric hospital with an endovascular surgery department.
- Timing: Planned hospitalization at 36–37 weeks in uncomplicated cases.
- Preparation: Mandatory central venous catheterization, creation of a cross-matched donor blood reserve, and readiness of an autologous blood recovery device.
Briefly: answers to topical questions
What are the main stages of surgical treatment for true placenta accreta during organ-sparing surgeries?
The main stages of organ-sparing surgery for true placenta accreta include delivery of the fetus, temporary arrest of blood flow, and removal of the affected area.
- Access and fetal delivery — median laparotomy and fundal cesarean section are performed. The fetus is delivered through an incision in the uterine fundus (away from the placental site), the placenta is left untouched, the umbilical cord is ligated and placed back into the uterine cavity, and the incision is sutured.
- Temporary hemostasis — balloon occlusion of the uterine or common iliac arteries is performed.
- Removal and reconstruction — resection of the uterine area with the adherent placenta (metroplasty) is performed, followed by suturing of the uterine defect.
Additionally, comprehensive compression hemostasis and automated autologous erythrocyte reinfusion are used.
What clinical symptoms are characteristic of morbidly adherent placenta during an attempted manual removal?
When attempting manual removal of a pathologically adherent placenta, the main clinical symptom is the inability to separate it from the uterine wall.
- Difficulty of separation — partial or complete tissue resistance when trying to deliver the placenta.
- Inability to separate (Placenta accreta) — the placenta is firmly fused to the uterine wall, making both spontaneous and manual delivery impossible.
If this sign is detected in the third stage of labor, the attempt at manual removal must be stopped immediately to avoid massive hemorrhage. The pathology has no specific clinical signs, but uterine bleeding is often the leading symptom.
What is the technique of endovascular surgery for placenta previa and accreta?
The technique of endovascular surgery for placenta accreta involves temporary balloon occlusion or vessel embolization.
- Temporary balloon occlusion of the common iliac arteries — bilateral puncture of the common femoral arteries is performed with the introduction of introducers. Guidewires are placed into the abdominal aorta, through which balloons are advanced to the level of the bifurcation and inflated to 4 atm. Occlusion time is 10–20 minutes.
- Uterine artery embolization — catheterization is performed via the femoral and internal iliac arteries, followed by the administration of 510–700 micron embolic particles under angiographic guidance.
Temporary balloon occlusion provides complete cessation of blood flow, minimization of blood loss, and conditions for more thorough surgical hemostasis.
Class and exam questions
What is the difference between placenta adherens and placenta accreta?
In placenta accreta, due to scar degeneration of the endometrium, the placenta does not separate spontaneously, but the villi do not penetrate the myometrium. In true placenta accreta (increta/percreta), the Nitabuch layer is destroyed, and the villi invade the muscular layer of the uterus or grow through it completely.
What are the main ultrasonographic signs of placenta accreta identified on ultrasound?
The main signs include the absence of the retroplacental hypoechoic zone, the presence of large vascular lacunae, hypervascularization of the lower uterine segment, and the absence of a clear boundary between the uterus and the urinary bladder.
To which type of hospital should a pregnant woman be referred when this pathology is suspected?
The patient is hospitalized in a Level III obstetric hospital in advance (at 36–37 weeks), and a mandatory requirement is the availability of an endovascular surgery department and the capability for autologous blood transfusion.
What else to study on this topic
- Pathogenetic mechanisms of increased proteolytic activity of chorionic villi
- Features of the differential diagnosis of placenta accreta, increta, and percreta using MRI
- The role of the HDliveflow mode in assessing lower uterine segment vascularization
- Organization of a multidisciplinary team and vascular surgeons during surgery
- Autologous blood donation and collection techniques in massive blood loss
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