Beta-blockers in Pregnancy Don't Cause Fetal Heart Defects: Study

Marlene Busko

April 20, 2017

PASADENA, CA — In a large cohort of pregnant women covered by insurance, those who received beta-blockers—mainly labetalol for hypertension—did not have a greater risk of having a baby with a congenital heart defect than other women, after adjustment for differences between the two groups of women[1].

"While these findings do not definitively rule out the possibility of fetal congenital defects in association with beta-blocker use, these results do provide reassurance regarding the use of this class of medication for the treatment of cardiac conditions in pregnant women," Lewel Duan (Kaiser Permanente Southern California, Pasadena) and colleagues report in a research letter published online April 17, 2017 in JAMA Internal Medicine.

Although beta-blockers are the most commonly used class of medication to treat cardiac conditions in pregnant women, a recent meta-analysis reported that this drug class was associated with congenital heart defects in neonates, Duan and colleagues note[2].

They identified 379,238 women in a Kaiser Permanente Southern California database who gave birth between 2003 and 2014.

Of these women, 4847 women (1.3%) had filled a prescription for a beta-blocker during their pregnancy.

Most of these women had been prescribed labetalol (3357 women, 69%) and fewer had received atenolol (638 women, 13%), propranolol (489 women, 10%), metoprolol (324 women, 7%), or another beta-blocker (39 women, 0.01%).

About half of the women who had received a beta-blocker had taken this drug during the first trimester (2628 women, 54%).

Compared with the other pregnant women, those who had filled a prescription for a beta-blocker during pregnancy were older (mean age 33 vs 30) and had a higher body-mass index (32 vs 26).

They were also more likely to have hypertension (75% vs 7%), hyperlipidemia (28% vs 10%), type 2 diabetes (18% vs 4%), heart failure (3% vs 0.3%), arrhythmia (19% vs 4%), or chronic kidney disease (5.1% vs 0.5%).

In addition, they were more likely to have preeclampsia (1.9% vs 0.6%) or eclampsia (0.5% vs 0.1%) and deliver a neonate with a higher mean birthweight (811 v s 554 g) but a younger mean gestational age (37.4 vs 38.9 weeks).

In unadjusted analyses, compared with not receiving a beta-blocker, women who took a beta-blocker during pregnancy were significantly more likely to have a neonate with a congenital cardiac anomaly such as a septal defect (P<0.001).

However, after adjustment for maternal age, body-mass index, and comorbidities and gestational age at delivery, the mothers who received a beta-blocker in the first trimester or at any time during their pregnancy did not have an increased risk of having an infant with a congenital heart defect (P=0.93 and P=0.32, respectively).

Some women may not have taken the drugs after they filled the prescriptions, Duan and colleagues acknowledge. On the other hand, analyzing dispensed prescriptions avoids recall bias.

The results suggest that the associations between maternal beta-blocker use and fetal heart defects were due to the characteristics of the pregnant women rather than the beta-blockers that the women took.

Thus, "the previously reported association between beta-blocker use and fetal cardiac anomalies in other studies may be attributed to confounding," according to the researchers.

The authors report no relevant financial relationships.

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