Midtrimester Rupture of Membranes

Midtrimester rupture of membranes is rupture of the amniotic sac between 14 and 27 weeks and 6 days. It often follows infection, cervical insufficiency, amniocentesis, bleeding or cervical surgery. It carries a high risk of pregnancy loss, infection and pulmonary hypoplasia, though some women reseal and continue to term.

• Many women labour within weeks of rupture.
• Risk factors: previous preterm birth, short cervix, cerclage, smoking, genital infection, polyhydramnios, bleeding.
• Fluid may reaccumulate in a minority.

Women have sudden leakage of fluid or constant wetness, with little pain, and may notice a smaller bump. Fever, abdominal tenderness and offensive discharge point to infection.

• Reduced fundal height.
• Contractions begin in a proportion.
• Differential diagnosis: urinary incontinence, vaginal discharge, cervical insufficiency with bulging membranes, bacterial vaginosis, threatened miscarriage.
• Complications: chorioamnionitis, maternal sepsis, abruption, cord prolapse, pulmonary hypoplasia, limb contracture, fetal death, extremely preterm birth.

The approach is to confirm rupture, measure fluid and exclude infection and labour.

• Sterile speculum with pooling and nitrazine paper (pH above 6.5); placental alpha microglobulin 1 or insulin-like growth factor binding protein 1 test where available.
• Ultrasound: amniotic fluid index, deepest vertical pocket, fetal weight, cervical length, lung to head ratio and thoracic circumference in specialist units.
• Temperature, pulse, full blood count, C-reactive protein, high vaginal and rectovaginal swab, urine culture.
• Cardiotocography after 24 weeks.

The principle is antibiotics and expectant care for stable women, with steroids after viability and delivery for infection.

• Supportive: admit for the first 1 week and then consider home care with temperature twice daily if stable and fluid is not progressively falling; pelvic rest; avoid digital examination; counselling on survival and disability; remove any cerclage for infection or labour.
• 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); betamethasone 12 mg IM twice, 24 hours apart, from 24 weeks to 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; nifedipine 20 mg oral once then 10 to 20 mg every 6 to 8 hours for up to 48 hours for contractions in a woman without infection; chorioamnionitis: ampicillin 2 g IV 6-hourly plus gentamicin 5 mg/kg IV once daily; paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours).
• Procedures: induction of delivery for infection, abruption, labour or maternal wish within the law, using misoprostol 400 micrograms vaginal 3-hourly (maximum 5 doses), with mifepristone 200 mg oral 24 to 48 hours earlier where available; delivery at 34 weeks and 0 days for women who reach it; caesarean section for obstetric reasons after viability.
• Special groups: RhD negative women give anti-D immunoglobulin 500 IU IM within 72 hours of bleeding; women with HIV continue tenofovir 300 mg, lamivudine 300 mg and dolutegravir 50 mg oral once daily; women with a cerclage have it removed at 34 weeks, or earlier for infection or labour.
• Red flags: fever, foul liquor, uterine tenderness, bleeding, pulse above 100 per minute, contractions, reduced fetal movements.
• Follow-up: full blood count and C-reactive protein twice weekly; amniotic fluid index weekly; growth scan every 2 weeks; counselling for the next pregnancy including cervical length scans and progesterone.