Rupture of membranes before labor is called premature rupture of membranes (PROM). The reported incidence varies, accounting for 2.7% to 17% of total childbirths. It occurs approximately 2.5 to 3 times more frequently in premature labor than in full-term labor. Its adverse effects on pregnancy and childbirth include an increased rate of premature labor, higher perinatal mortality, and elevated rates of intrauterine and puerperal infections.

bubble_chart Etiology

Trauma; cervical incompetence; pregnancy late stage [third stage] where sexual intercourse causes mechanical stimulation or leads to chorioamnionitis; lower genital tract infections caused by bacteria, viruses, or toxoplasma; increased intra-amniotic pressure (e.g., multiple pregnancies, polyhydramnios); poor engagement of the fetal presenting part with the pelvic inlet (e.g., cephalopelvic disproportion, abnormal fetal position, etc.); and poor development of the fetal membranes leading to thinness and fragility.

bubble_chart Clinical Manifestations

A pregnant woman suddenly feels a large amount of fluid flowing out from the vagina, followed by intermittent small discharges.

Impact on mother and child: Premature rupture of membranes (PROM) can cause mental stress for the mother, may induce premature labor, and increase the risk of intrauterine infection and puerperal infection. For those who give birth more than 48 hours after membrane rupture, the maternal infection rate is 5–20%, the sepsis rate is 1:145, and the maternal mortality rate is approximately 1:5500. Fetal aspiration of infected amniotic fluid can lead to fetal pneumonia or fetal distress; even asymptomatic cases may result in congenital neonatal pneumonia after childbirth. The risk of umbilical cord prolapse also increases. Some reports indicate a neonatal mortality rate of 1.7% after correction for early membrane rupture. The closer to full-term pregnancy, the higher the likelihood of labor onset after membrane rupture. Generally, membrane rupture does not affect the progress of labor.

When intra-abdominal pressure increases, such as during coughing, sneezing, or bearing heavy loads, amniotic fluid leaks out. If the amount of fluid increases when the presenting part of the fetus is pushed upward during a rectal examination, a definitive diagnosis can be made.

1. Vaginal fluid pH test: Normally, vaginal fluid has a pH of 4.5–5.5, amniotic fluid has a pH of 7.0–7.5, and urine has a pH of 5.5–6.5. When tested with nitrazine paper, if the vaginal fluid is alkaline with a pH ≥7.0, it is considered positive, strongly suggesting amniotic fluid and a high likelihood of premature rupture of membranes (PROM).

2. Vaginal fluid smear examination: If dried smears of the fluid show fern-like crystals, it indicates amniotic fluid. Smears stained with 0.5% methylene blue reveal pale yellow or unstained fetal skin epithelial cells and lanugo; smears stained with Sudan III show orange-yellow fat globules, and those stained with 0.5% Nile blue sulfate reveal yellowish fetal epithelial cells. These results are more reliable than pH test strips and can confirm the presence of amniotic fluid.

3. Amnioscopy: Direct visualization of the presenting part of the fetus without seeing the forebag of amniotic fluid confirms the diagnosis of PROM.

bubble_chart Treatment Measures

1. Pregnant women with premature rupture of membranes should be hospitalized for delivery, closely monitoring changes in fetal heart sounds. Those without engagement of the presenting part should rest absolutely in bed, preferably in a lateral position, to prevent umbilical cord prolapse. If labor has already begun, the progression of labor should not be hindered.

3. If labor has not begun and there are no signs of infection, and the fetus has reached full term (37 weeks of gestation with a fetal weight of at least 2500g), observation for 12–18 hours is advisable. If labor does not commence, induction or cesarean section should be initiated based on the situation.

4. If gestational age is less than 37 weeks, there are no signs of labor or infection, maintain perineal hygiene and closely monitor to allow for appropriate prolongation of pregnancy.

5. If the pregnancy is preterm but labor has begun with a cephalic presentation, vaginal delivery may be attempted.

6. If the pregnancy is preterm but beyond 30 weeks of gestation, and breech labor has begun, cesarean section should be considered. However, if the mother disagrees, it should not be forced. For pregnancies less than 30 weeks, vaginal delivery is preferable.

7. After childbirth, antibiotics should be administered to control infection.

bubble_chart Prevention

Actively prevent and treat lower genital tract infections, and emphasize hygiene guidance during pregnancy; prohibit sexual intercourse in the late stage of pregnancy [third stage]; avoid heavy lifting and abdominal impact; for those with cervical incompetence, bed rest is recommended, and cervical cerclage should be performed around 14 weeks of pregnancy, with the cerclage site as close as possible to the level of the internal cervical os. Regarding whether to prophylactically administer antibiotics after membrane rupture, most scholars believe that prophylactic use of Yaodui has minimal effect on reducing maternal morbidity and does not reduce perinatal morbidity or mortality. Additionally, antibiotics crossing the placenta may lead to neonatal drug resistance in the future. Therefore, it is advocated to actively treat postpartum rather than prophylactically use antibiotics.