Zhuang Tingting, Zhang Yu, Ren Xueli, Pan Qixin, Sun Jingli
Postgraduate Training Base of Jinzhou Medical University (General Hospital of Northern Theater Command), No.83, Wenhua Road, Shenhe District, Shenyang, 110016, China.
Department of Obstetrics and Gynecology, General Hospital of Northern Theater Command, No.83, Wenhua Road, Shenhe District, Shenyang, 110016, China.
BMC Pregnancy Childbirth. 2025 Mar 11;25(1):275. doi: 10.1186/s12884-025-07373-x.
The association between interpregnancy interval (IPI) after vaginal delivery and preterm birth (PTB) in singleton has not been elucidated. The aim of this study is to investigate the association between interpregnancy interval after vaginal delivery and preterm birth.
Birth data from the 2022 National Vital Statistics System (NVSS) were selected, and multinomial logistic regression models were used to determine the odds ratios (OR) and 95% confidence intervals (95% CI) for the association between IPI after vaginal delivery and PTB. A restricted cubic spline (RCS) model with multivariate adjustment was constructed with a 4-node OR curve to check for possible non-linear relationships. Threshold effect analysis was conducted using two-piecewise linear regression and a likelihood ratio test.
The study included a total of 1,517,106 subjects, with an average age of 30.56 ± 5.29 years. 113,613 subjects had PTB, while 1,403,493 did not. Compared to the reference group (18-23 months), IPI of ≤ 11 months and ≥ 24 months were associated with an increased risk of PTB. The RCS curve observed a J-shaped association between the IPI after vaginal delivery and PTB (P < 0.001), with the lowest point of PTB risk occurring at approximately 23 months. The effect values for < 23 months and ≥ 23 months were 0.975 (95% CI: 0.974 ~ 0.977, P < 0.001) and 1.006 (95% CI: 1.005 ~ 1.006, P < 0.001), respectively. The results of sensitivity analyses remained stable.
In patients with a history of vaginal delivery, a J-shaped non-linear relationship was found between the IPI and the risk of PTB. IPIs of ≤ 11 months and ≥ 24 months were associated with an increased risk of PTB.
单胎妊娠经阴道分娩后的妊娠间隔（IPI）与早产（PTB）之间的关联尚未阐明。本研究旨在探讨经阴道分娩后的妊娠间隔与早产之间的关联。
选取2022年国家生命统计系统（NVSS）的出生数据，采用多项逻辑回归模型确定经阴道分娩后的妊娠间隔与早产之间关联的比值比（OR）和95%置信区间（95%CI）。构建具有多变量调整的受限立方样条（RCS）模型及4节点OR曲线，以检查可能的非线性关系。使用两段式线性回归和似然比检验进行阈值效应分析。
该研究共纳入1,517,106名受试者，平均年龄为30.56±5.29岁。113,613名受试者发生早产，1,403,493名未发生早产。与参照组（18 - 23个月）相比，妊娠间隔≤11个月和≥24个月与早产风险增加相关。RCS曲线显示经阴道分娩后的妊娠间隔与早产之间呈J形关联（P < 0.001），早产风险最低点出现在约23个月时。<23个月和≥23个月时的效应值分别为0.975（95%CI：0.974～0.9
