Interpregnancy interval and the risk of adverse perinatal outcomes of singleton pregnancies: a retrospective analysis - 12/11/26

Doi : 10.1016/j.jogoh.2026.103322

Xinghe Bu ^1,^2,^{^{#
These authors contributed equally.}}, Wenjing Ye ^1,^2,^{^{#
These authors contributed equally.}}, Mengyue Zhang ^2,^3,^{^{#
These authors contributed equally.}}, Laishuan Wang ^1,^2,^⁎

¹ Department of Neonatology, Children’s Hospital of Fudan University, National Children’s Medical Center, Shanghai, 201102, China

² National Health Commission (NHC) Key Laboratory of Neonatal Diseases, Shanghai, 201102, China

³ Shanghai Children’s Hospital, Shanghai Jiao Tong University, 355 Lane Luding Rd, Putuo District, Shanghai 200062, China

^⁎ Corresponding author: Laishuan Wang, Department of Neonatology, Children’s Hospital of Fudan University, No.399, Wanyuan Road, 201102, Shanghai, China, Tel.: +86-13611843863 Department of Neonatology Children’s Hospital of Fudan University No.399, Wanyuan Road Shanghai 201102 China

Sous presse. Manuscrit accepté. Disponible en ligne depuis le Thursday 12 November 2026

Abstract

This retrospective study analyzed 3,568,957 singleton live births from the US National Vital Statistics System (2021-2022) to evaluate adverse perinatal outcomes (preterm birth, low birth weight, small for gestational age) using interpregnancy interval (IPI) as a continuous variable. Departing from conventional categorical classifications, we treated IPI as a continuous monthly variable to precisely delineate the full risk trajectory. Spline smoothing and logistic regression revealed that an IPI of 20 months had the lowest risk. Compared to this nadir, IPI <6 months increased odds by 44% (adjusted odds ratio=1.44, 95% CI 1.40-1.48) and IPI >120 months increased odds by 74% (aOR=1.74, 95% CI 1.70-1.78). Risk and incidence charts were generated for IPI as a continuous measure, including subgroups by prior preterm birth or cesarean section. Our findings confirm that both short and long IPIs are associated with elevated perinatal risks, with 20 months emerging as the optimal interval for subsequent pregnancy planning. These continuous-risk charts offer an evidence-based, practical resource to enhance prenatal counseling and family education.

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Highlights

•	Optimal interpregnancy interval identified as 20 months for lowest perinatal risk.
•	IPI ≤ 6 months is associated with 44% higher odds; ≥ 120 months with 74% higher odds. Risk incidence charts for continuous IPI, stratified by prior preterm birth/cesarean.
•	Spline smoothing and threshold analysis reveal optimal IPI of 20 months.