Superimposed Preeclampsia

Superimposed preeclampsia is preeclampsia that develops in a woman with chronic hypertension, shown by new proteinuria, sudden worsening of blood pressure, or new organ dysfunction after 20 weeks. It is common in women with chronic hypertension. It matters because it carries higher risks of abruption, growth restriction, preterm birth and stillbirth than either condition alone.

• Risk factors: long-standing hypertension, kidney disease, diabetes, obesity, age above 40 years, previous preeclampsia.
• Aspirin from 12 weeks lowers the risk.
• Blood pressure drugs must be changed before or early in pregnancy.

Women with known hypertension have a rise in blood pressure needing more drugs, new proteinuria, or headache, visual change, epigastric pain or oedema. Examination may show hyperreflexia and a small fundal height.

• Rise in blood pressure by 30/15 mmHg or more with new proteinuria.
• Sudden onset of severe features.
• Differential diagnosis: worsening chronic hypertension, kidney disease flare, lupus nephritis, renal artery stenosis, phaeochromocytoma, HELLP syndrome, thrombotic thrombocytopenic purpura.
• Complications: eclampsia, HELLP syndrome, abruption, stroke, heart failure, acute kidney injury, fetal growth restriction, preterm birth, stillbirth.

The diagnosis needs a new feature after 20 weeks in a woman with established hypertension.

• New or sudden increase in proteinuria (urine protein to creatinine ratio 30 mg/mmol or more, or doubled if baseline proteinuria exists), sudden rise in blood pressure, platelets below 100 x 10^9/L, liver enzymes twice the upper limit, creatinine rise, pulmonary oedema, or new neurological or visual symptoms.
• Full blood count, creatinine, liver enzymes, lactate dehydrogenase, uric acid, urine protein to creatinine ratio, coagulation screen; baseline tests early in pregnancy for comparison.
• Ultrasound for growth and umbilical artery Doppler; uterine artery Doppler at 20 to 24 weeks.
• Cardiotocography; ECG and echocardiography if there is heart disease.

The principle is to optimise drugs, control blood pressure, prevent seizures when severe, and deliver at 37 weeks or earlier depending on severity.

• Supportive: admit at diagnosis; left lateral rest; daily fetal movement counts; blood pressure 4-hourly; hourly urine output when severe; fluid limit of 80 mL per hour when severe; stop smoking.
• Pharmacological: aspirin 150 mg oral at night from 12 weeks to 36 weeks; 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; stop ACE inhibitors, angiotensin receptor blockers, spironolactone and thiazides; 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, before 34 weeks; oxytocin 10 IU IM after birth, avoiding ergometrine.
• Procedures: delivery at 37 weeks without severe features, and within 24 hours of stabilisation with severe features; induction with misoprostol 25 micrograms vaginal 6-hourly (maximum 4 doses) or Foley catheter, then oxytocin; caesarean section for obstetric reasons.
• Special groups: kidney disease reduces magnesium sulphate to 0.5 g per hour with level monitoring; diabetes needs insulin adjustment with steroids; women on enalapril before conception are changed to nifedipine or labetalol.
• Red flags: blood pressure 160/110 mmHg or more, headache, visual change, epigastric pain, seizure, platelets below 100 x 10^9/L, oliguria, reduced fetal movements.
• Follow-up: review twice weekly with blood tests; growth scans every 2 weeks from 28 weeks; postnatal blood pressure at 6 hours, daily for 5 days, then at 2 and 6 weeks; long term hypertension care.