Medically Indicated Preterm Birth

Medically indicated preterm birth is delivery before 37 weeks that clinicians plan because continuing the pregnancy puts the mother or fetus at greater risk than prematurity. Common reasons are preeclampsia, fetal growth restriction, abruption, placenta previa with bleeding, chorioamnionitis, intrahepatic cholestasis, fetal compromise and maternal illness. The timing balances the risk of staying pregnant against the risk of prematurity.

• Risk factors: chronic hypertension, diabetes, kidney disease, twin pregnancy, previous stillbirth, advanced maternal age.
• Steroids need about 48 hours to work fully, so delay is used when it is safe.
• Maternal or fetal deterioration overrides delay.

Features are those of the underlying condition, such as hypertension and proteinuria, small fundal height, bleeding, fever, itching or reduced fetal movements. Many women have no symptoms and the indication comes from monitoring.

• Blood pressure of 160/110 mmHg or more, absent end diastolic flow, abnormal cardiotocography or bleeding are common triggers.
• Mother is often not in labour.
• Differential diagnosis: spontaneous preterm labour, threatened preterm labour, term pregnancy with wrong dates, reversible cause of the abnormal finding.
• Complications: prematurity, respiratory distress syndrome, neonatal hypoglycaemia, intraventricular haemorrhage, caesarean section, maternal morbidity from the underlying disease, stillbirth if delivery is delayed.

The approach is to confirm the indication and the stability of mother and fetus before deciding the timing.

• Blood pressure, urine protein to creatinine ratio, full blood count, creatinine, liver enzymes, lactate dehydrogenase, bile acids, glucose, coagulation screen as indicated.
• Ultrasound for growth, liquor, umbilical artery and middle cerebral artery Doppler, ductus venosus Doppler; cardiotocography.
• Cervical examination and Bishop score to choose induction or caesarean section.
• Confirm gestation from the earliest scan.

The principle is to give steroids and magnesium sulphate, stabilise the mother and deliver at the time set by the condition.

• Supportive: admit to a unit with neonatal intensive care; left lateral position; two cannulae; blood group and cross-match; continuous cardiotocography; counselling; delayed cord clamping for 30 to 60 seconds.
• Pharmacological: 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 (with calcium gluconate 1 g IV over 10 minutes for toxicity), and for preeclampsia with severe features at any gestation for 24 hours after birth; labetalol 20 mg IV over 2 minutes then 40 mg, 80 mg and 80 mg at 10 minute intervals (maximum 220 mg) or nifedipine immediate release 10 mg oral repeated once after 30 minutes for blood pressure of 160/110 mmHg or more; ursodeoxycholic acid 300 mg oral 8-hourly for intrahepatic cholestasis; oxytocin 10 IU IM at birth.
• Procedures: delivery at once for eclampsia, abruption, HELLP syndrome, pulmonary oedema, chorioamnionitis or pathological cardiotocography; delivery 24 to 48 hours after the first steroid dose for stable women; delivery at 34 weeks for severe preeclampsia or absent end diastolic flow, at 30 to 32 weeks for reversed end diastolic flow, at 36 weeks for placenta previa with bleeding and at 35 to 36 weeks for intrahepatic cholestasis with bile acids of 100 micromol/L or more; induction with misoprostol 25 micrograms vaginal 6-hourly (maximum 4 doses) or a Foley catheter with a 30 mL balloon when the cervix is unfavourable and the fetus is stable, and caesarean section when delivery is urgent or vaginal birth is unlikely within 24 hours.
• Special groups: diabetes needs insulin increased by 25 to 40 percent for 72 hours after steroids; kidney disease reduces magnesium sulphate to 0.5 g per hour with level monitoring.
• Red flags: seizure, blood pressure of 160/110 mmHg or more, bleeding, fever, fetal bradycardia, absent or reversed end diastolic flow, falling platelets.
• Follow-up: neonatal intensive care or kangaroo mother care; maternal blood pressure and blood tests until normal; review at 6 weeks; preconception and early pregnancy plan, including aspirin 150 mg oral at night from 12 weeks to 36 weeks where preeclampsia was the cause.