Adverse maternal outcomes associated with major fetal malformations after singleton live birth

Major fetal malformations complicate 2% to 5% of live births. It is unclear what effect fetal malformations have on severe maternal morbidity.

This study aimed to compare maternal outcomes between individuals with a fetus with major or minor fetal malformations and those with a fetus without major or minor fetal malformations.

This was a secondary analysis of the Consortium on Safe Labor database. Our study was limited to the current analysis of pregnant individuals with a singleton live birth. Major fetal malformations based on the Centers for Disease Control and Prevention's criteria were defined. Fetal malformations that did not meet the criteria for major fetal malformations were categorized as minor fetal malformations. Our primary maternal outcome was severe maternal morbidity as defined by the Centers for Disease Control and Prevention. Missing values were imputed by multiple imputation using the k-nearest neighbor imputation method. Poisson regression with robust error variance was used to obtain adjusted relative risks with 95% confidence intervals, controlling for confounders.

Of 216,881 deliveries, there were 201,860 cases (93.1%) with no congenital malformation, 12,106 cases (5.6%) with minor fetal malformations, and 2845 cases (1.3%) with major fetal malformations. Compared with individuals with no fetal malformation, those with major fetal malformations were more likely to have severe maternal morbidity (0.7% vs 1.2%; adjusted relative risk, 1.51; 95% confidence interval, 1.07-2.12), postpartum hemorrhage (3.6% vs 6.9%; adjusted relative risk, 1.76; 95% confidence interval, 1.50-2.06), preeclampsia (5.1% vs 8.3%; adjusted relative risk, 1.48; 95% confidence interval, 1.31-1.67), and cesarean delivery (26.7% vs 42.3%; adjusted relative risk, 1.51; 95% confidence interval, 1.45-1.58). Compared with individuals with no fetal malformation, those with minor fetal malformations were more likely to have severe maternal morbidity (0.7% vs 1.4%; adjusted relative risk, 1.73; 95% confidence interval, 1.48-2.02), maternal death (0.01% vs 0.03%; adjusted relative risk, 4.50; 95% confidence interval, 1.18-17.19), postpartum hemorrhage (3.6% vs 6.1%; adjusted relative risk, 1.54; 95% confidence interval, 1.41-1.68), preeclampsia (5.1% vs 8.6%; adjusted relative risk, 1.50; 95% confidence interval, 1.41-1.60), superimposed preeclampsia (1.2% vs 2.4%; adjusted relative risk, 1.25; 95% confidence interval, 1.14-1.38), cesarean delivery (26.7% vs 39.6%; adjusted relative risk, 1.38; 95% confidence interval, 1.35-1.41), chorioamnionitis (3.0% vs 4.7%; adjusted relative risk, 1.41; 95% confidence interval, 1.29-1.53), and postpartum endometritis (0.6% vs 1.0%; adjusted relative risk, 1.58; 95% confidence interval, 1.31-1.90).

Major and minor congenital fetal malformations are independent risk factors for severe maternal morbidity and other pregnancy complications.