Preterm labour and preterm prelabour rupture of membranes

Gestational context

22 to 37 weeks

booking

12w

anatomy

24w

28w

36w

term

Maternal

Contractions: frequency and change over an hour
Temperature, heart rate, uterine tenderness for chorioamnionitis: Temperature, heart rate, uterine tenderness for chorioamnionitis
Speculum: pooling, cervical change, swabs
Antibiotics for PPROM latency; magnesium under 32 weeks for the fetus: Antibiotics for PPROM latency; magnesium under 32 weeks for the fetus

Fetal

Gestation decides everything: steroids, magnesium, place of birth
Heart rate and tachycardia as an early sign of infection: Heart rate and tachycardia as an early sign of infection
Presentation and estimated weight on ultrasound: Presentation and estimated weight on ultrasound
Neonatal team briefed before, not after: Neonatal team briefed before, not after

Preterm labour

Diagnosis: regular contractions with cervical change before 37 weeks. Most who present with contractions are not in labour; the tests that help are cervical length (over 30 mm: unlikely) and fetal fibronectin (negative: unlikely to deliver within 7 to 14 days).
Antenatal corticosteroids (betamethasone 12 mg intramuscularly, two doses 24 hours apart) from 24+0 to 34+6 weeks when delivery within 7 days is likely: they reduce respiratory distress, intraventricular haemorrhage and death. A single rescue course may be given later. Late preterm steroids (34 to 36+6) are considered case by case.
Magnesium sulfate for neuroprotection when delivery is expected before 32 weeks (SOGC: up to 33+6): it reduces cerebral palsy.
Tocolysis (nifedipine first line; indomethacin before 32 weeks) for up to 48 hours to complete steroids and transfer to a centre with the right neonatal unit. It does not prolong pregnancy meaningfully beyond that and is contraindicated with infection, abruption or fetal compromise.
GBS prophylaxis in labour if the status is positive or unknown.
Prevention for the next pregnancy: vaginal progesterone for a short cervix; cerclage for a history of cervical insufficiency.

Preterm, admitted with contractions. A reassuring preterm strip. The accelerations look modest but meet the preterm definition (10 by 10 before 32 weeks), so the strip is reactive and Category I.Read it in the lab

PPROM

Diagnosis: history of a gush, then a sterile speculum examination showing pooling in the posterior fornix; nitrazine (alkaline) and ferning support it, and a placental alpha-microglobulin test where available. Avoid digital examination: it adds nothing and shortens the latency to delivery.
Risks: chorioamnionitis, cord prolapse, abruption, preterm delivery, pulmonary hypoplasia if very early with oligohydramnios.
Management 24 to 33+6 weeks: admit, steroids, latency antibiotics (ampicillin and erythromycin or azithromycin) to prolong latency and reduce infection, magnesium if delivery threatens before 32, surveillance for infection (temperature, maternal and fetal heart rates, uterine tenderness, CBC, monitoring). No tocolysis.
34 to 36+6 weeks: expectant management versus delivery is a discussion; practice is moving towards expectant management to 37 weeks in the absence of infection, with GBS prophylaxis.
Chorioamnionitis at any gestation: broad-spectrum antibiotics and delivery.

Ferning

Amniotic fluid dries into a fern-like crystal pattern under the microscope; cervical mucus can too, so ferning is read with the pooling and the history, never alone.

Check

29 weeks, regular painful contractions every 5 minutes, cervix 2 cm and 60 percent effaced, membranes intact, no fever. Which three things happen in the next hour?

On the modelCervix Amnion and membranes Isthmus and lower segment