Abstract

Preterm birth (PTB) remains a leading cause of neonatal morbidity and mortality globally. A prior PTB is a recognized predictor of recurrence; nonetheless, most existing studies have limited their focus to the first two pregnancies. We aimed to evaluate the risk of recurrent PTB across three consecutive singleton pregnancies. This retrospective cohort study analyzed data from 97,854 women with singleton pregnancies. Participants were stratified based on the gestational age at their first delivery, and PTB outcomes in subsequent pregnancies were assessed. Additionally, a sub-analysis of 11,760 women with three consecutive deliveries was conducted to assess the cumulative risk of recurrent PTB. The adjusted relative risk (aRR) for PTB was estimated using multivariable models. Among the study population, 12.3% (n=12,036) experienced PTB in their first pregnancy, of which 10.1% were spontaneous and 2.2% were medically indicated. The risk of PTB in the second pregnancy demonstrated an inverse relationship with gestational age at the first delivery: 8.6% for term, 19% for 34–36⁶ weeks, 25.9% for 32–33⁶ weeks, and 29.3% for deliveries under 32 weeks. The aRR for PTBs in the second pregnancy were 3.72 (34–36⁶ weeks), 5.65 (32–33⁶ weeks) and 6.21 (

Key words: Gestational age, pregnancy outcomes, preterm birth, recurrent preterm birth, protective factors