Chronic Hypertension in Pregnancy

Hypertension present before pregnancy, or diagnosed before 20 weeks gestation, or persisting beyond 12 weeks postpartum. Increases the risk of superimposed pre-eclampsia (roughly 25%), fetal growth restriction, and placental abruption.

Usually asymptomatic; the key clinical task is medication review at booking, since several commonly used antihypertensives are unsafe in pregnancy.

BP ≥140/90 mmHg before 20 weeks, or a pre-existing diagnosis; distinguished from gestational hypertension and pre-eclampsia principally by timing of onset.

• Stop ACE inhibitors, ARBs, and thiazide diuretics at conception or as soon as pregnancy is confirmed, given teratogenicity and fetotoxicity, particularly ACE inhibitor/ARB associated oligohydramnios and renal dysgenesis with second and third trimester exposure
• Switch to labetalol, nifedipine, or methyldopa at the doses detailed under Gestational Hypertension
• Treatment target under 135/85 mmHg
• Aspirin 75 to 150 mg PO od from 12 weeks, since chronic hypertension is itself a high risk criterion for pre-eclampsia prophylaxis
• Increased surveillance for superimposed pre-eclampsia (regular urine protein and bloods) and serial growth scans from around 28 weeks given elevated FGR risk
• Postpartum: continue antihypertensives, reviewing choice if breastfeeding (labetalol, nifedipine, and enalapril are generally considered compatible)

Referral: obstetric-led care; maternal medicine input for poorly controlled or complicated hypertension.