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CME Credit Offered
CME Credit Offered
Abstract Award
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Poster Session 1

(209) Association of Chorionicity and Severe Maternal Morbidity in Twin Pregnancies

Thursday, January 30, 2025
10:30 AM – 12:30 PM  
Objective: Twin gestations are associated with higher risks for adverse neonatal and perinatal outcomes, with chorionicity known to influence these risks. However, the impact of chorionicity on severe maternal morbidity (SMM) is unclear. This study assessed the risk of SMM and obstetric complications by chorionicity in twin gestations.

Study Design: Population-based, retrospective cohort study of U.S. delivery hospitalizations from 2015-2021 using the National Inpatient Sample database. ICD-10 codes identified delivery hospitalizations, chorionicity, and outcomes. SMM was defined by the CDC criteria (excluding transfusion) and individual indicators grouped by organ system. The primary objective was to compare SMM risk by chorionicity in twin versus singleton gestations, with secondary analysis of obstetric complications. Adjusted relative risks (aRR) and 95% confidence intervals (CI) were estimated using multivariate logistic regression.

Results: Of 22,482,597 delivery hospitalizations, 98.5% were singleton, 0.3% monochorionic and 1.2% dichorionic twins. SMM risk was higher in mono- (1.9%, aRR 2.07, 95% CI 1.81-2.37) and dichorionic (2.3%, aRR 2.38, 95% CI 2.23-2.53) gestations compared to singletons (0.8%), however, composite SMM did not vary by chorionicity. Eclampsia, thromboembolic SMM, and hysterectomy risk was significantly increased in dichorionic twins (aRR 2.25, 95% CI 1.84-2.76; aRR 1.51, 95% CI 1.13-2.01; aRR 2.31, 95% CI 1.99-2.68) compared to singletons, but did not differ by chorionicity (Figure 1). Cesarean section risk was elevated in both mono- (aRR 8.43, 95% CI 8.09-8.79) and dichorionic (aRR 8.89, 95% CI 8.69-9.10) twins compared to singletons. Monochorionicity had the highest risk for vasa previa (aRR 8.25, 95% CI 6.43-10.6) and intrauterine fetal demise (aRR 8.93, 95% CI 8.29-9.63), while dichorionicity had the highest risk of severe preeclampsia (aRR 3.22, 95% CI 3.12-3.31) (Figure 2).

Conclusion: SMM risk is higher in twin gestations compared to singletons, but SMM risk is not altered by chorionicity. This is valuable information for maternal counseling in the setting of twin pregnancy.