397: Fetal growth patterns in women with maternal arrhythmias treated with beta blockers

Abstract

We sought to evaluate the association between fetal growth and BB use in patients with stable maternal arrhythmias. This was a retrospective cohort analysis (IRB#15-405) comparing 35 singleton pregnancies complicated by maternal arrhythmias treated with BBs between 2006 and 2019 to 35 matched singleton pregnancies not affected by arrhythmia or BB use. Controls were matched by maternal age +/- 3 years, gestational age (GA) at delivery +/- 10 days, and race. Patients with structurally abnormal hearts, chronic hypertension, preeclampsia prior to 34 weeks GA, diabetes, and autoimmune disorders were excluded. Our outcomes of interest were estimated fetal weight (EFW) percentile values by third trimester ultrasound and BW percentiles. Variables were compared using Student's T-test. We found that the mean growth of the entire cohort was normal, with normal EFW and BW percentiles (57.74% +/- 27.42 and 51.23% +/- 30.82 with BB use and 47.42% +/- 21.60 and 56.94% +/- 23.20 in the control group respectively). The percentage of FGR infants were 5.7% (N=2) and 0.0% in the BB and control groups respectively, which is not statistically different from the general population. Both cases of FGR were associated with metoprolol use. There was no difference in burden of adverse events as defined by NICU stay, neonatal demise/stillbirth, placental abruption, or chorioamnionitis between groups. In this cohort of women with maternal arrhythmia treated with BBs, there was no significant difference in fetal growth patterns from the control group. This suggests that BB use may not be an independent risk factor for FGR as many indications for their use are confounding. These findings should be further explored in a larger cohort.