Severe Maternal Morbidity in Pregnancies Complicated by Fetal Congenital Heart Disease.

Background: Maternal risk factors for fetal congenital heart disease (CHD) may also be associated with delivery complications in the mother.

Objectives: This study aimed to determine the prevalence of and risk factors for severe maternal morbidity (SMM) and maternal hospital transfer in pregnancies complicated by fetal CHD.

Methods: A population-based retrospective cohort study utilizing linked Ohio birth certificates and birth defect data for all live births from 2011 to 2015 was performed. The primary outcome was composite SMM. Secondary outcome was maternal hospital transfer prior to delivery. Pregnancies with isolated fetal CHD were compared to pregnancies with no fetal anomalies and isolated fetal cleft lip/palate (CLP).

Results: A total of 682,929 mothers with live births were included. Of these, 5,844 (0.85%) mothers had fetal CHD, and 963 (0.14%) had fetal CLP. SMM in pregnancies with fetal CHD was higher than that in those with no anomalies (3.6% vs 1.9%,  < 0.001) or CLP (3.6% vs 1.9%,  = 0.006). After adjusting for known risk factors, fetal CHD remained independently associated with SMM when compared to no fetal anomalies (adjusted relative risk [adjRR]: 1.81, 95% CI: 1.58-2.08) and CLP (adjRR: 1.81, 95% CI: 1.12-2.92). Maternal hospital transfer occurred more frequently in fetal CHD cases vs for those without fetal anomalies with an increased adjusted risk (adjRR: 3.65, 95% CI: 3.14-4.25).

Conclusions: Pregnancies with isolated fetal CHD have increased risk of SMM and maternal hospital transfer after adjusting for known risk factors. This may inform delivery planning for mothers with fetal CHD. Understanding the biological mechanisms may provide insight into other adverse perinatal outcomes in this population.