Treatment with oral beta-blockers during pregnancy complicated by maternal heart disease increases the risk of fetal growth restriction

Objective: To investigate the effect on fetal growth of treatment with oral beta-blockers during pregnancy in women with congenital or acquired heart disease.

Design: Historical matched cohort study.

Setting: Centre for Pregnant Women with Heart Disease, Copenhagen University Hospital, Denmark.

Population: A cohort of 175 women with heart disease, grouped according to beta-blocker treatment, and a cohort of 627 women from the overall population matched on seven birthweight-determining factors.

Methods: Differences between groups were tested by simple descriptive statistics and assessed using standard hypothesis tests. Associations were estimated by correlational analysis and multivariable regression.

Main outcome measure: Proportion of infants born small for gestational age (SGA).

Results: More of the infants exposed to beta-blockers were SGA compared with non-exposed infants (29.4 versus 15.3%; P < 0.05). After adjustment for birthweight-determining factors, beta-blocker treatment and maternal body mass index (BMI) were the only factors independently associated with SGA (the relative difference in expected birthweight was -8.6%; 95% CI -13.3 to -3.9%; P = 0.0004). After adjustment for BMI, beta-blocker treatment was associated with an increased risk of SGA (OR 2.65; 95% CI 1.15-6.10; P = 0.02). In a subgroup with isolated tachyarrhythmias, SGA infants were more frequent in the beta-blocker exposed group compared with the non-exposed group (31 versus 10%; P < 0.005). Beta-blocker treatment was the only independent predictor of SGA, adjusting for several factors influencing fetal growth (the relative difference in expected birthweight was -12.2%; 95% CI -19.9 to -3.9%; P = 0.001).

Conclusions: In a historical cohort of pregnancies complicated by maternal heart disease, treatment with beta-blockers was found to be independently associated with an increased risk of delivering an SGA infant.