Preterm Birth After Membrane Rupture

Preterm birth after membrane rupture is birth before 37 weeks following rupture of the amniotic sac before labour (preterm prelabour rupture of membranes). It results from infection, inflammation, cervical insufficiency, bleeding or overdistension. It is responsible for a large share of preterm births, and delivery often follows within a week of rupture. It matters because infection, cord prolapse, abruption and prematurity must be managed together.

• Risk factors: previous preterm rupture, genital infection, smoking, short cervix, bleeding, polyhydramnios, multiple pregnancy.
• The earlier the rupture, the longer the latency and the higher the risk of pulmonary hypoplasia.
• Antibiotics lengthen latency and lower infection.

Women report a gush or trickle of fluid, often with few contractions at first. Fever, tenderness and foul liquor signal infection.

• Pooling of liquor on speculum examination.
• Contractions often begin within days.
• Differential diagnosis: urinary incontinence, vaginal discharge, loss of mucus plug, bacterial vaginosis, preterm labour with intact membranes.
• Complications: chorioamnionitis, cord prolapse, abruption, preterm labour, pulmonary hypoplasia, neonatal sepsis, respiratory distress syndrome, neonatal death, maternal sepsis.

The approach is to confirm rupture, assess infection and fetal condition and decide the time of birth.

• Sterile speculum: pooling, nitrazine paper blue (pH above 6.5), ferning; placental alpha microglobulin 1 or insulin-like growth factor binding protein 1 test where available.
• Ultrasound for gestation, presentation, estimated fetal weight, amniotic fluid index and deepest pocket.
• Temperature and pulse 4-hourly, full blood count and C-reactive protein twice weekly, high vaginal and rectovaginal swab, urine culture, cardiotocography.
• Avoid digital examination unless labour is established.

The principle is antibiotics, steroids, magnesium sulphate when birth is near, and delivery at 34 weeks or earlier for infection.

• Supportive: admit; pelvic rest; temperature 4-hourly; pad checks; fetal movement counts; delayed cord clamping for 60 seconds; kangaroo mother care; transfer to a unit with neonatal intensive care if below 34 weeks.
• Pharmacological: amoxicillin 500 mg oral 8-hourly plus erythromycin 250 mg oral 6-hourly for 7 days (azithromycin 1 g oral once if erythromycin is unavailable; avoid amoxicillin-clavulanate); betamethasone 12 mg IM twice, 24 hours apart, between 24 weeks and 34 weeks and 6 days; magnesium sulphate 4 g IV over 20 minutes then 1 g per hour until delivery for 24 hours at most, before 32 weeks, when birth is expected within 24 hours; benzylpenicillin 5 million units IV then 2.5 million units 4-hourly in labour for group B streptococcus; ampicillin 2 g IV 6-hourly plus gentamicin 5 mg/kg IV once daily for chorioamnionitis; nifedipine 20 mg oral once then 10 to 20 mg oral every 6 to 8 hours for up to 48 hours to complete steroids when there is no infection; oxytocin 10 IU IM at birth; newborn benzylpenicillin 50 mg/kg IV 12-hourly plus gentamicin 5 mg/kg IV 24-hourly (36-hourly below 32 weeks) pending cultures, and surfactant (poractant alfa 200 mg/kg endotracheal, then 100 mg/kg) for respiratory distress.
• Procedures: induction or caesarean section at 34 weeks and at once for infection, abruption, cord prolapse or fetal compromise; vaginal birth for a cephalic baby; caesarean section for malpresentation; amnioinfusion with sodium chloride 0.9 percent 500 mL over 30 minutes then 3 mL per minute for variable decelerations with oligohydramnios.
• Special groups: RhD negative women with bleeding give anti-D immunoglobulin 500 IU IM within 72 hours; HIV positive women continue tenofovir 300 mg, lamivudine 300 mg and dolutegravir 50 mg oral once daily; penicillin allergy with a severe reaction uses clindamycin 900 mg IV 8-hourly.
• Red flags: temperature above 38 degrees Celsius, maternal pulse above 100 per minute, fetal heart rate above 160 beats per minute, foul liquor, bleeding, uterine tenderness, palpable cord.
• Follow-up: neonatal intensive care; maternal temperature 4-hourly for 24 hours after birth; review at 6 weeks; cervical length scans and progesterone in the next pregnancy.