Late-Onset Preeclampsia

Late onset preeclampsia is preeclampsia diagnosed at 34 weeks or later. It reflects a mismatch between placental capacity and maternal and fetal demand, with a normally grown fetus in most cases. It accounts for most preeclampsia and usually has milder maternal and perinatal outcomes than early onset disease, though severe forms do occur.

• Risk factors: first pregnancy, obesity, diabetes, chronic hypertension, twin pregnancy, age above 35 years.
• Delivery at 37 weeks is usually appropriate for mild disease.
• Severe disease needs stabilisation then prompt delivery.

Women are often asymptomatic, with hypertension and proteinuria at routine antenatal visits. Others have headache, swelling, visual change or epigastric pain.

• Normal fundal height in most.
• Sudden weight gain above 1 kg per week.
• Differential diagnosis: gestational hypertension, chronic hypertension, kidney disease, urinary tract infection, acute fatty liver of pregnancy, HELLP syndrome.
• Complications: eclampsia, HELLP syndrome, abruption, pulmonary oedema, postpartum haemorrhage, acute kidney injury, stillbirth.

The diagnosis follows standard criteria at 34 weeks or later.

• Blood pressure 140/90 mmHg or more on two readings 4 hours apart with proteinuria (urine protein to creatinine ratio 30 mg/mmol or more) or organ dysfunction.
• Full blood count, creatinine, liver enzymes, lactate dehydrogenase, uric acid, urine protein to creatinine ratio, coagulation screen if platelets are below 100 x 10^9/L.
• Ultrasound for growth and liquor volume with umbilical artery Doppler; cardiotocography.
• Repeat blood tests every 48 to 72 hours for mild disease.

The principle is blood pressure control, prevention of seizures if severe, and timely delivery.

• Supportive: admit for assessment; left lateral rest; blood pressure 4-hourly; daily fetal movement counts; fluid limit of 80 mL per hour if severe.
• Pharmacological: 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) or methyldopa 250 to 500 mg oral 8-hourly (maximum 3 g daily), aiming for 110 to 135/85 mmHg; for 160/110 mmHg or more give 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); magnesium sulphate 4 g IV over 20 minutes then 1 g per hour for 24 hours for severe features; betamethasone 12 mg IM twice, 24 hours apart, only before 34 weeks and 6 days when delivery is planned; oxytocin 10 IU IM after birth, avoiding ergometrine.
• Procedures: induction of labour at 37 weeks for non-severe disease, and within 24 hours of stabilisation for severe disease, using misoprostol 25 micrograms vaginal 6-hourly (maximum 4 doses) or a Foley catheter with a 30 mL balloon and oxytocin 2 mU/minute doubling every 30 minutes to 32 mU/minute; caesarean section for obstetric reasons.
• Special groups: asthma uses nifedipine instead of labetalol; diabetes needs insulin adjustment when steroids are given.
• Red flags: blood pressure 160/110 mmHg or more, severe headache, visual change, epigastric pain, seizure, platelets below 100 x 10^9/L, oliguria, reduced fetal movements.
• Follow-up: antenatal review twice weekly; postpartum blood pressure at 6 hours, daily for 5 days, then at 2 and 6 weeks; urine protein and kidney function at 6 weeks.