Role of Antihypertensive Treatment and Blood Pressure Control in the Occurrence of Adverse Pregnancy Outcomes: A Population-Based Study of Linked Electronic Health Records

Background: Chronic hypertension (CH) adversely impacts pregnancy. It remains unclear whether antihypertensive treatment alters these risks. We examined the role of antihypertensive treatment in the association between CH and adverse pregnancy outcomes. Methods: Electronic health records from the UK Caliber and Clinical Practice Research Datalink were used to define a cohort of women delivering between 1997 and 2016. Primary outcomes were preeclampsia, preterm birth (PTB), and fetal growth restriction (FGR). We used multivariable logistic regression to compare outcomes in women with CH to women without CH and propensity score matching to compare antihypertensive agents. Results: The study cohort consisted of 1 304 679 women and 1 894 184 births. 14 595 (0.77%) had CH, and 6786 (0.36%) were prescribed antihypertensive medications in pregnancy. Overall, women with CH (versus no CH), had higher odds of preeclampsia (adjusted odds ratio [aOR], 5.74 [95% CI, 5.44-6.07]); PTB (aOR, 2.53 [2.39-2.67]); and FGR (aOR, 2.51 [2.31-2.72]). Women with CH prescribed treatment (versus untreated women) had higher odds of preeclampsia (aOR, 1.17 [1.05-1.30]), PTB (1.25 [1.12-1.39]), and FGR (1.80 [1.51-2.14]). Women prescribed methyldopa (versus β-blockers) had higher odds of preeclampsia (aOR, 1.43 [1.19-1.73]); PTB (1.59 [1.30-1.93]), but lower odds of FGR (aOR, 0.66 [0.48-0.90]). Odds of adverse outcomes were similar in relation to calcium channel blockers (versus β-blockers) except for PTB (aOR, 1.94 [1.15-3.27]). Among women prescribed treatment, lower average blood pressure (<135/85 mm Hg) was associated with better pregnancy outcomes. Conclusions: Treatment with antihypertensive agents and control of hypertension ameliorates some effects but higher risks of adverse outcomes persist. β-Blockers versus methyldopa may be associated with better pregnancy outcomes except for FGR. Powered trials are needed to inform optimal treatment of CH during pregnancy.