Maternal low body mass index is a risk factor for fetal ductal constriction following indomethacin use among women undergoing fetal repair of spina bifida

Objectives: The objectives were to determine the prevalence of and to identify risk factors associated with constriction of the fetal ductus arteriosus (DA) following perioperative indomethacin use for fetal myelomeningocele (MMC) repair. Study design. A retrospective chart review study included 100 consecutive fetuses who underwent fetal MMC repair between 2011 and 2018. All patients had fetal echocardiography (FE) on postoperative day (POD)#1 and 2 to detect constriction of the DA. All patients received indomethacin for tocolysis using a standardized protocol. Multivariate regression analysis was carried out to identify the predictors for fetal ductal constriction. Results: Eighty patients met our study eligibility criteria. Median gestational age at time of surgery was 25 (24-25) weeks. Constriction of the DA was detected in 14 fetuses (17.5%). In five fetuses, this was observed on POD# 1, in seven on POD# 2, and in two on both days. The only independent risk factor for predicting DA constriction was maternal body mass index (BMI) <25 kg/m² (P =.002). Conclusion: Indomethacin therapy following fetal MMC surgery requires careful daily FE surveillance. The association of DA constriction and low BMI suggests that BMI-based dosing of indomethacin may be recommended for perioperative tocolysis in fetal MMC surgery.