Hydralazine administration in pregnancy may cause which of the following effects?

• A. Reflex tachycardia and fetal bradycardia with uteroplacental insufficiency; headaches; delayed maternal hypotension
• B. Hyperkalemia and fetal hypertension
• C. Severe hyperglycemia in the mother
• D. Seizures in the mother and fetus

Answer: (A)

Hydralazine works by directly dilating arterioles, which lowers systemic vascular resistance. That vasodilation triggers the maternal body to respond with reflex sympathetic activity, often leading to rapid heart rate (reflex tachycardia) and headaches from the sudden drop in vascular tone.

If the maternal blood pressure falls too much, placental blood flow can be reduced, causing uteroplacental insufficiency. That decreased placental perfusion can distress the fetus, and in some cases may present as fetal bradycardia on monitoring.

Headache is a common accompanying sign due to vasodilation, and the blood pressure reduction can occur with a delay relative to the dose in some situations.

Other effects listed—hyperkalemia, fetal hypertension, severe maternal hyperglycemia, and seizures—are not typical associations with hydralazine in pregnancy.