The effect of beta-blockers on foetal birth weight in pregnancies in women with structural heart disease: a prospective cohort study

Objective: To examine whether treatment with beta-blockers (BBs) in pregnant women with structural heart disease (SHD) resulted in a decrease in foetal birth weight (FBW) in a South African cohort. Methods: This was a prospective cohort study conducted in a tertiary-level hospital in Cape Town from 2010 to 2016. Of the 178 pregnant women with SHD, 24.2% received BBs for a minimum of two weeks. Adverse foetal outcomes and mean FBW were compared between the BB groups and subgroups (congenital, valvular, cardiomyopathy and other). Adverse foetal outcome was defined as: low birth weight (LBW) < 2 500 g, Apgar score < 7, premature birth (< 37 weeks) and small for gestational age (SGA). Results: BB exposure during pregnancy was found to be associated with a non-significant increased FBW (2 912 vs 2 807 g, p = 0.347). A significant decrease (p = 0.009) was noted in FBW for valvular SHD pregnancies using BBs, while a significant increase (p = 0.049) was observed for the same outcome in the cardiomyopathy subgroup using BBs. A significant increase was observed for SGA (p = 0.010) and LBW (p = 0.003) pregnancies within the valvular subgroup when exposed to BBs. Conclusion: BB use in pregnant women with SHD in a South African cohort showed no association with a decrease in FBW or an increase in adverse foetal outcomes when compared to non-BB usage.