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The following is a summary of “Association between interpregnancy interval and adverse perinatal outcomes among subsequent twin pregnancies: a nationwide population-based study,” published in the July 2024 issue of Obstetrics and Gynecology by Ye et al.

The existing evidence on the relationship between interpregnancy interval (IPI) and pregnancy outcomes largely focuses on singleton pregnancies, with limited research addressing twin pregnancies. This study aims to fill that gap by investigating the association between IPI and adverse perinatal outcomes specifically in twin pregnancies.

This population-based, retrospective cohort study utilized data from the National Center for Health Statistics (NCHS) in the United States from 2016 to 2020. The study included multiparous women aged 18 to 45 years who gave birth to live-born twins without congenital anomalies between 26 and 42 weeks of gestation. Using Poisson regression models adjusted for potential confounders, researchers evaluated the associations between IPI and several adverse outcomes, including preterm birth (PTB) before 36 weeks, small for gestational age (SGA), neonatal intensive care unit (NICU) admission, neonatal composite morbidity, and infant death. Missing data on covariates were handled with multiple imputations. Dose-response analyses were conducted using the restricted cubic splines (RCS) approach, and subgroup analyses were stratified by maternal age, parity, and combination of neonatal sex. Sensitivity analyses were performed using complete data and by excluding pregnancies with intervening events during the IPI.

The analysis included 143,014 twin pregnancies. Compared to the referent group with an IPI of 18-23 months, an IPI of less than 6 months was associated with a significantly increased risk of PTB before 36 weeks (RR, 1.21; 95% CI: 1.17-1.25), SGA (RR, 1.11; 95% CI: 1.03-1.18), neonatal composite morbidity (RR, 1.19; 95% CI: 1.12-1.27), NICU admission (RR, 1.18; 95% CI: 1.14-1.22), and infant death (RR, 1.29; 95% CI: 1.05-1.60). An IPI of 5 years or more was similarly associated with an increased risk of PTB before 36 weeks (RR, 1.18; 95% CI: 1.15-1.21), SGA (RR, 1.24; 95% CI: 1.18-1.30), neonatal composite morbidity (RR, 1.10; 95% CI: 1.05-1.15), and NICU admission (RR, 1.14; 95% CI: 1.11-1.17). 

Dose-response analyses revealed U-shaped or J-shaped associations between these outcomes and IPI. Variations in associations were observed based on advanced maternal age, parity, and neonatal sex combination. Sensitivity analyses supported the robustness of these findings.

In conclusion, extreme IPIs—less than 6 months or more than 5 years—are associated with adverse outcomes in twin pregnancies. Therefore, IPI could serve as a valuable predictor for risk stratification in high-risk twin pregnancies, aiding in clinical decision-making and patient counseling.

Source: sciencedirect.com/science/article/pii/S2589933324001654