Exposure to beta-blockers during the first trimester of pregnancy was not associated with heightened risk for cardiac or other major birth defects, analysis of two large cohorts found.
The excess risks with such exposure were not significant for major congenital malformations (adjusted RR 1.07, 95% CI 0.89-1.30) or cardiac malformations (aRR 1.12, 95% CI 0.83-1.51), reported Brian Bateman, MD, MSc, of Brigham and Women's Hospital in Boston, and colleagues in Annals of Internal Medicine.
The absolute excess risks per 1,000 persons exposed were 3.0 (95% CI -6.6 to 12.6) and 2.1 (95% CI -4.3 to 8.4), respectively, which at the very least excluded a large increase, the researchers noted.
"In the setting of small numbers of outcomes, our study cannot exclude an increase in the RR for the less common malformation types, cleft lip or palate and CNS malformations," they cautioned. "However, the point estimates from our analysis suggest a more modest increase in the RR for these malformations than earlier publications have reported."
Those prior studies had significant limitations like bias and confounding by the mother's hypertension, Bateman and co-authors emphasized. The present study restricted the assessment to pregnancies with a diagnosis of hypertension in order to lessen potential confounding by indication.
"The potential risks to the fetus must be balanced against the risks to the mother associated with untreated hypertension," they concluded.
Maternal health is a priority for clinicians and parents, Joel Ray, MD, MSc, of University of Toronto, agreed in an accompanying editorial. "Moreover, fetal well-being depends on maternal well-being, and untreated maternal disease both jeopardizes the health of a fetus and may shorten a pregnancy," the editorialist wrote.
"Accordingly, beta-blockers should be used in pregnancy when indicated for the treatment of various maternal medical conditions, and labetalol should be a first-line treatment choice for chronic hypertension," Ray continued.
The study was reassuring, said Stephen Chasen, MD, of Weill Cornell Medicine in New York City, who was not involved in the study.
"If there is any impact, it is likely to be very small. Since uncontrolled hypertension can be associated with very poor outcomes during pregnancy, we can be confident that preventing maternal morbidity with beta-blockers even in the earliest stages of pregnancy is safe, and that the clear benefits are very likely to outweigh any theoretical risk," Chasen told MedPage Today.
Bateman's group evaluated 3,577 women in a Nordic cohort with hypertensive pregnancies, of whom 19.1% were exposed to beta-blockers in the first trimester. The group consisted of women from Denmark, Finland, Iceland, Norway, and Sweden who had a pregnancy with a single, live-born infant.
The study also looked at the U.S. MAX database of all hypertensive pregnant women aged 12 to 55 years continuously receiving Medicaid from the 3 months prior to their last menstrual cycle to 1 month after delivery. Of the 14,900 women in this group, 11.2% were exposed to beta-blockers in the first trimester.
For cleft lip or palate, the pooled adjusted relative risk linked with beta-blockers was 1.97 (95% CI 0.74-5.25), and the risk difference per 1,000 persons (RD1000) exposed was 1.0 (95% CI -0.9 to 3.0).
For central nervous system malformations, the aRR was 1.37 (95% CI 0.58-3.25) and the RD1000 was 1.0 (95% CI -2.0 to 4.0).
The main limitation of the study was that it was retrospective. "Hypertensive women who require blood pressure medication are different than hypertensive women who don't," Chasen highlighted.
Another one of the study's limitations was that the U.S. population assessed was not representative of the entire obstetric population, he added.
"Future studies should examine the risk associated with individual beta-blockers and how it may vary with dose," the investigators said.
The study was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Söderström König Foundation, the National Institute of Mental Health, Finnish Medicines Agency, the National Institute for Health and Welfare, and the Social Insurance Institution of Finland.
Bateman disclosed relationships with the National Institutes of Health, Lilly, GlaxoSmithKline, Baxalta, Pacira, and Pfizer.
Ray did not disclose any conflicts of interest.
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