Prescription of antihypertensive medications during pregnancy in the UK

Abstract

Purpose: This study aimed to describe the management of antihypertensive medications in pregnancy by general practitioners in the UK and compare it with current guidelines.

Methods: We used electronic medical records from The Health Improvement Network database from 1996 to 2010 to identify completed pregnancies. The study cohort included the first pregnancy identified during the study period in women aged 13-49 years. Information on both hypertension diagnoses and prescription of specific antihypertensive medications within the 90 days before the last menstrual period (LMP) and during pregnancy was ascertained from electronic medical records.

Results: Among 148,544 eligible pregnancies, we identified 1995 (1.3%) during which the women had pre-existing hypertension diagnosed by the LMP date. Overall, the prevalence of antihypertensive medications during the first trimester was 1.5%; beta-blockers were the most commonly prescribed antihypertensive. Among women with pre-existing hypertension, 36% were prescribed an antihypertensive medication during the 90 days before the LMP. Among those, 9.6% and 22.2% had discontinued their medication by the first and second trimesters, respectively. For contraindicated drugs such as angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, the corresponding discontinuation rates were around 25% and 70%. Women who switched therapy received preferably either methyldopa or an alpha/beta-blocker.

Conclusions: In this population of UK pregnant women, prescription patterns of antihypertensive medications were dominated by recommended treatments, although some patients continued on contraindicated drugs throughout pregnancy or switched to preferred agents in a delayed fashion.

Keywords: THIN; antihypertensive medications; hypertension; pharmacoepidemiology; pregnancy; treatment patterns.