Preterm Birth Due to Preeclampsia

Preterm birth due to preeclampsia is delivery before 37 weeks to protect the mother and the fetus from preeclampsia, which is the commonest medical reason for preterm delivery. It is chosen when blood pressure cannot be controlled, organ function falls, or the fetus is at risk. The aim is to deliver the mother before serious harm while giving the baby the benefit of steroids when time allows.

• Preeclampsia with severe features before 34 weeks needs inpatient care in a unit with neonatal intensive care.
• Risk factors: first pregnancy, chronic hypertension, kidney disease, diabetes, antiphospholipid syndrome, twin pregnancy, previous preeclampsia.
• Magnesium sulphate lowers the risk of eclampsia.

Women have hypertension and proteinuria, sometimes with headache, visual change, epigastric pain, vomiting or oedema. Others have no symptoms and the indication comes from tests.

• Blood pressure of 160/110 mmHg or more.
• Hyperreflexia and clonus.
• Differential diagnosis: gestational hypertension, chronic hypertension with superimposed preeclampsia, HELLP syndrome, acute fatty liver, thrombotic thrombocytopenic purpura, lupus nephritis.
• Complications: eclampsia, stroke, HELLP syndrome, abruption, pulmonary oedema, acute kidney injury, liver haematoma, growth restriction, prematurity and its complications, maternal death.

The approach is to document severity, maternal organ function and fetal condition.

• Blood pressure every 15 minutes during acute treatment, then 4-hourly; urine protein to creatinine ratio.
• Full blood count and film, creatinine, liver enzymes, lactate dehydrogenase, uric acid, coagulation screen, fibrinogen, group and cross-match; repeat every 6 to 12 hours in severe disease.
• Ultrasound for growth, liquor, umbilical artery and middle cerebral artery Doppler; cardiotocography.
• Bishop score for the route of birth.

The principle is magnesium sulphate, blood pressure control, steroids and delivery by the safest route once the mother is stable.

• Supportive: admit to high dependency care; left lateral position; two cannulae; urinary catheter with hourly output; total fluids 80 mL per hour; oxygen if saturation is below 94 percent; delayed cord clamping for 60 seconds if the baby is vigorous.
• Pharmacological: magnesium sulphate 4 g IV over 20 minutes then 1 g per hour for 24 hours after birth (stop for absent patellar reflexes, respiratory rate below 12 per minute or urine below 30 mL per hour, with calcium gluconate 1 g IV over 10 minutes for toxicity); 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, or hydralazine 5 mg IV then 5 to 10 mg every 20 to 30 minutes (maximum 20 mg) to reach 140 to 150/90 to 100 mmHg; maintenance labetalol 200 mg oral every 8 to 12 hours (maximum 2.4 g daily) or nifedipine modified release 30 to 60 mg oral once daily (maximum 120 mg); betamethasone 12 mg IM twice, 24 hours apart, between 24 weeks and 34 weeks and 6 days; oxytocin 10 IU IM at birth, avoiding ergometrine.
• Procedures: delivery at once for eclampsia, HELLP syndrome, abruption, pulmonary oedema, uncontrolled hypertension or fetal compromise; delivery 24 to 48 hours after the first steroid dose if mother and fetus are stable; delivery at 34 weeks for severe features; 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 delivery is not urgent; caesarean section when birth is urgent and the cervix is unfavourable, or before 32 weeks with a very unfavourable cervix; platelet transfusion of one adult dose for platelets below 50 x 10^9/L before caesarean section.
• Special groups: kidney disease reduces magnesium sulphate to 0.5 g per hour with level monitoring; asthma uses nifedipine instead of labetalol; platelets below 70 x 10^9/L contraindicate spinal anaesthesia.
• Red flags: seizure, blood pressure of 160/110 mmHg or more despite two drugs, oxygen saturation below 94 percent, oliguria, falling platelets, bleeding, fetal bradycardia.
• Follow-up: high dependency care for 24 to 48 hours after birth; blood pressure at 6 hours, daily for 5 days, then at 2 and 6 weeks; blood tests daily until normal; aspirin 150 mg oral at night from 12 weeks to 36 weeks in the next pregnancy.