Neonatal effects of intrauterine metoprolol/bisoprolol exposure during the second and third trimester: a cohort study with two comparison groups.

OBJECTIVES

Our aim was to evaluate the effects of beta-blockers during the second and third trimester on fetal growth, length of gestation and postnatal symptoms in exposed infants.

METHODS

The current prospective observational cohort study compares 294 neonates of hypertensive mothers on metoprolol or bisoprolol during the second and/or third trimester with 225 methyldopa-exposed infants and 588 infants of nonhypertensive mothers. The risks for reduced birth weight, prematurity, neonatal bradycardia, hypoglycaemia and respiratory disorders were analysed.

RESULTS

The rate of small-for-gestational-age children was significantly higher in long-term beta-blocker exposed infants (24.1%) compared with the methyldopa cohort [10.2%, odds ratio (OR)adj 2.5, 95% confidence interval (CI) 1.2-5.2] and the nonhypertensive cohort (9.9%, ORadj 4.3, 95% CI 2.6-7.1). The risk for preterm birth was significantly increased compared with nonhypertensive pregnancies (ORadj 2.2, 95% CI 1.3-3.8) but not compared with the methyldopa cohort. Neonatal adverse outcomes occurred more frequently in the study cohort (11.5%) compared with the nonhypertensive comparison group (6.5%) and the methyldopa cohort (8.4%), but without statistical significance (ORadj 1.5, 95% CI 0.7-3.0 and ORadj 1.5, 95% CI 0.7-3.3, respectively).

CONCLUSION

Long-term intrauterine exposure to metoprolol or bisoprolol may increase the risk of being born small-for-gestational-age. It is still a matter of debate to which extent maternal hypertension contributes to the lower birth weight. Serious neonatal symptoms are rare. Altogether, metoprolol and bisoprolol are well tolerated treatment options, but a case-by-case decision on close neonatal monitoring is recommended.