Diagnosis of threatened miscarriage
Assessment of the patient's condition begins with a careful vaginal examination. Important rule: inserting the index finger into the cervical canal is strictly prohibited. The physician evaluates the softening and shortening of the cervix, its position along the pelvic axis, and the low presentation of the fetal part, which stretches the lower uterine segment.
A combination of methods is used for objective confirmation of the diagnosis:
- Laboratory test: detection of phosphorylated insulin-like growth factor-binding protein 1 in cervical mucus. A positive result indicates a high risk of imminent delivery, while a negative result provides a "safe window" with low risk for the next 7–14 days.
- Transvaginal sonography (TVS): warning signs include a cervical length of less than 25 mm and dilation of the cervical canal.
- Tocography: allows recording of increased myometrial tone and the presence of contractions.
Tocolytic therapy
The main goal in a threatened condition is to prolong the pregnancy. For this purpose, medications that suppress uterine contractions (tocolytics) are used. There are three types of tocolysis:
- Acute: emergency cessation of contractions for transporting a pregnant woman to a Level III hospital or in case of acute fetal hypoxia.
- Massive: rapid administration of drugs when labor has already begun. The objective is to gain at least 48 hours for medical preparation of the fetal lungs (up to 34 weeks).
- Prolonged: maintenance of the effect at early gestational ages after successfully stopping the acute threat.
Several drug groups are available in the physician's arsenal:
- Selective $\beta_2$-adrenomimetics (e.g., hexoprenaline). Require strict monitoring of the mother's blood pressure, pulse, diuresis, and blood glucose levels, as they can cause tachycardia, hypotension, and pulmonary edema.
- Oxytocin receptor antagonists (atosiban). Prescribed in a course of no more than 48 hours with cervical dilation from 1 to 3 cm and normal fetal heart rate.
- Calcium channel blockers (nifedipine). Suppress uterine activity, require monitoring of pulse and blood pressure.
- Progesterone preparations (dydrogesterone, vaginal micronized progesterone).
Fetal protection and concomitant treatment
If stopping labor entirely is impossible, all efforts are directed toward increasing the viability of the preterm infant.
- Prevention of respiratory distress syndrome (RDS): corticosteroids are administered intramuscularly to pregnant women before 34 weeks (betamethasone 12 mg twice every 24 hours or dexamethasone 6 mg four times every 12 hours). They stimulate surfactant production, increase pulmonary tissue elasticity, and reduce neonatal mortality. The optimal effect develops after 48 hours.
- Neuroprotection: magnesium sulfate is used up to 32 weeks of gestation. It protects the fetal brain and reduces the likelihood of developing cerebral palsy. During infusion, diuresis is strictly monitored (discontinued if it drops below 30 mL/h) along with maternal reflexes.
- Antibiotic therapy: prescribed strictly according to indications (detected pathogenic flora, bacterial vaginosis, asymptomatic bacteriuria) with mandatory simultaneous restoration of normal vaginal biocenosis.
Peculiarities of gentle delivery
Preterm labor should take place exclusively in Level III hospitals with a neonatal intensive care unit and readiness for resuscitation in the delivery room (availability of an incubator, oxygen, surfactant). The main principle is the most gentle management possible to prevent cerebral trauma in the fetus.
- Pain management: epidural analgesia is considered the optimal method. It not only relieves pain but also relaxes the pelvic floor muscles, reducing trauma to the infant and uterine hyperactivity.
- Expulsion stage: the parturient woman lies on her side to slow down the advancement of the fetal head. Classical manual perineal support is strictly prohibited. Surgical episiotomy is indicated to facilitate crowning.
- Cesarean section: abdominal delivery is performed in breech presentation or extreme fetal conditions (acute hypoxia, hydrops fetalis).
Briefly: answers to topical questions
What maternal parameters must be monitored during magnesium sulfate infusion?
During magnesium sulfate infusion, it is necessary to monitor:
- pulse and blood pressure;
- respiratory rate — greater than 12 breaths per minute;
- oxygen saturation — 95–100%;
- deep tendon reflexes, e.g., knee reflexes;
- diuresis — at least 30 mL/h.
Monitoring of pulse, blood pressure, respiratory rate, and deep tendon reflexes is performed at least every 4 hours. Fetal heart rate monitoring is also carried out.
What are the absolute contraindications to tocolytic therapy?
Contraindications to tocolytic therapy include conditions requiring emergency delivery, as well as severe maternal and fetal pathologies. These include:
- Fetal factors — intrauterine fetal demise and congenital malformations incompatible with life.
- Maternal and obstetric factors — severe preeclampsia, hemorrhage with hemodynamic instability, chorioamnionitis, placental abruption, uterine scar incompetence, cervical dilation greater than 4 cm.
- Specific factors — preterm premature rupture of membranes at a gestational age greater than 32 weeks and the presence of medical contraindications to a specific drug.
What are the main etiological factors of threatened miscarriage in the first trimester?
In the first trimester, threatened miscarriages are often caused by chromosomal abnormalities, detected in 50–80% of embryos upon cytogenetic testing. Risk factors also include unfavorable socioeconomic and psychoemotional conditions, unemployment, and single-parent households. Most etiological factors impair trophoblast migration into the spiral arteries, which impedes the physiological development of the placenta and embryo/fetus, and can lead to pregnancy loss.
For quick memorization of the criteria for onset of preterm labor, use the "4–20–3" rule: 4 regular contractions per 20 minutes with cervical dilation up to 3 cm.
Class and exam questions
How to clinically distinguish threatened preterm labor from established preterm labor?
In a threatened condition, the patient is bothered by cramping pain and cervical shortening, but contractions are irregular. Onset of labor is characterized by a clear rhythm (4 contractions per 20 minutes) and objective cervical effacement with dilation up to 3 cm.
What is the diagnostic value of the phosphorylated insulin-like growth factor-binding protein 1 (phIGF-BP1) test?
This specific protein enters the cervical mucus only upon separation of the fetal membranes from the decidua. Its detection serves as an accurate marker of a high risk of imminent delivery.
Why is the classic perineal protection prohibited during the second stage of preterm labor?
Standard manual obstetric maneuvers create additional resistance and pressure on the fragile cranial bones of the preterm fetus. This sharply increases the risk of severe intracranial trauma.
What else to study on this topic
- Dosage regimens and management of side effects of $\beta_2$-adrenomimetics (hexoprenaline).
- Maternal monitoring algorithm during tocolysis with nifedipine and magnesium sulfate.
- Indications and administration regimens of progesterone preparations for pregnancy prolongation.
- Peculiarities of primary resuscitation of a preterm newborn in the delivery room.
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