Severe maternal morbidity and obstetrical outcomes by twin chorionicity and amnionicity

Twin gestations are associated with increased risks for adverse neonatal and perinatal outcomes. Chorionicity and amnionicity influence these risks however, their impact on severe maternal morbidity (SMM) remains incompletely understood.

To evaluate the risk of severe maternal morbidity and obstetric complications by twin type compared with singleton gestations.

Population-based, retrospective cohort study of U.S. delivery hospitalizations from 2015 to 2021 using the National Inpatient Sample database. ICD-10 codes identified delivery hospitalizations, twin type, and outcomes. SMM was defined by the CDC criteria (excluding transfusion) and individual indicators were grouped by organ system. The primary objective was to evaluate SMM across twin types compared to singleton gestations, with secondary outcomes including specific SMM indicators and obstetrical complications. Adjusted odds ratios (aOR) and 95% confidence intervals (CI) were estimated using multivariate logistic regression.

Of 22,506,417 delivery hospitalizations, 22,157,332 (98.49%) were singleton pregnancies, 4005 (0.02%) were monochorionic monoamniotic twins (MCMA), 68,085 (0.30%) monochorionic diamniotic twins (MCDA), and 268,330 (1.19%) dichorionic diamniotic twins (DCDA). Composite severe maternal morbidity (SMM) was more frequent in both MCDA (1.9%; crude OR: 2.54, 95% CI, 2.23-2.88) and DCDA (2.3%; crude OR: 2.99, 95% CI, 2.82-3.17) twin gestations compared with singletons (0.8%). Composite SMM increased with chorionicity among twin pregnancies, while estimates among MCMA twins were limited by small sample size. DCDA twins had significantly increased risks of hemorrhage-associated SMM (crude OR: 4.26, 95% CI, 4.09-4.44), hysterectomy (crude OR: 2.98, 95% CI, 2.57-3.45), cesarean delivery (crude OR: 6.51, 95% CI, 6.37-6.65), and preeclampsia with severe features (crude OR: 3.67, 95% CI, 3.57-3.77). MCMA twin pregnancies demonstrated the highest risk of intrauterine fetal demise compared with singleton gestations (crude OR: 22.49, 95% CI, 18.36-27.56).

SMM risk is higher in twin gestations compared to singletons with risk varying by chorionicity. This is valuable information for maternal counseling in the setting of twin pregnancy. VIDEO ABSTRACT.