Membrane Rupture with Infection

Membrane rupture with infection is rupture of the amniotic sac with intra-amniotic infection (chorioamnionitis), shown by fever and signs of infection of the membranes, liquor and fetus. It results from ascending vaginal organisms, including Escherichia coli, group B streptococcus, Bacteroides and genital mycoplasmas. It matters because it causes maternal sepsis, neonatal sepsis, preterm birth and fetal death, and delivery is needed whatever the gestation.

• Complicates preterm rupture more often than term rupture.
• Risk factors: prolonged rupture, repeated vaginal examinations, prolonged labour, group B streptococcus, bacterial vaginosis, internal fetal monitoring.
• Treatment starts as soon as the diagnosis is made, without waiting for cultures.

Women have fever of 38 degrees Celsius or more, rigors, abdominal pain, offensive vaginal discharge or liquor, and a tender uterus, with a fast pulse and fetal tachycardia.

• Maternal pulse above 100 per minute.
• Fetal heart rate above 160 beats per minute for 10 minutes.
• Differential diagnosis: urinary tract infection, pyelonephritis, malaria, appendicitis, pneumonia, epidural fever, viral illness, endometritis.
• Complications: maternal sepsis and shock, postpartum haemorrhage, uterine atony, endometritis, wound infection, neonatal sepsis, pneumonia, meningitis, cerebral palsy, stillbirth.

The diagnosis is clinical: fever with two or more of maternal tachycardia, fetal tachycardia, uterine tenderness, foul-smelling liquor or a raised white cell count.

• Temperature, pulse, blood pressure, respiratory rate and urine output; speculum examination for liquor colour and smell.
• Full blood count (white cells above 15 x 10^9/L), C-reactive protein, blood cultures, urine culture, high vaginal and rectovaginal swab, malaria test, lactate.
• Cardiotocography for fetal tachycardia and reduced variability; ultrasound for amniotic fluid index and presentation.
• Amniocentesis (glucose below 1.1 mmol/L, positive Gram stain or culture) in specialist units for preterm cases of doubt.

The principle is IV antibiotics at once and delivery by the quickest safe route.

• Supportive: admit to a high dependency area; two cannulae; Ringer's lactate 1 litre over 2 hours then 125 mL per hour; oxygen if saturation is below 94 percent; paracetamol and cooling; hourly urine output; continuous cardiotocography; senior obstetric, anaesthetic and neonatal team called.
• Pharmacological: ampicillin 2 g IV 6-hourly plus gentamicin 5 mg/kg IV once daily, started within 1 hour and continued until delivery, then for 24 hours after fever settles; add metronidazole 500 mg IV 8-hourly or clindamycin 900 mg IV 8-hourly after caesarean section; for severe sepsis give ceftriaxone 2 g IV once daily plus metronidazole 500 mg IV 8-hourly, and noradrenaline 0.05 micrograms/kg/minute IV titrated for mean arterial pressure of 65 mmHg or more; paracetamol 1 g oral or IV 6-hourly (maximum 4 g in 24 hours); oxytocin infusion starting at 2 mU/minute doubling every 30 minutes to 32 mU/minute for induction or augmentation; oxytocin 10 IU IM at birth with tranexamic acid 1 g IV over 10 minutes if bleeding exceeds 500 mL; betamethasone 12 mg IM twice, 24 hours apart, below 34 weeks only if it does not delay birth.
• Procedures: delivery as soon as possible by induction or augmentation, with caesarean section for obstetric reasons or fetal compromise; neonatal resuscitation team present.
• Special groups: penicillin allergy of low risk uses ceftriaxone 2 g IV once daily plus metronidazole 500 mg IV 8-hourly, and severe allergy uses clindamycin 900 mg IV 8-hourly plus gentamicin 5 mg/kg IV once daily; renal impairment uses ceftriaxone instead of gentamicin; newborns have a sepsis screen and benzylpenicillin 50 mg/kg IV 12-hourly plus gentamicin 5 mg/kg IV 24-hourly for 7 days when infection is confirmed.
• Red flags: systolic blood pressure below 90 mmHg, respiratory rate above 24 per minute, lactate above 2 mmol/L, oliguria, confusion, fetal bradycardia, bleeding.
• Follow-up: maternal temperature and pulse hourly in labour then 4-hourly for 48 hours; newborn sepsis surveillance for 48 hours; review at 1 week and 6 weeks for endometritis.