Risk of preterm birth in a twin pregnancy after an early‐term birth in the preceding singleton pregnancy: a retrospective cohort study

Abstract : Objective To evaluate whether a history of spontaneous early‐term birth (37+0–38+6 weeks of gestation) in the previous singleton pregnancy is a risk factor for preterm birth (PTB) in a subsequent twin pregnancy. Design Retrospective cohort study. Settings Two French university hospitals (2006–2016). Population All women who delivered twins from 24+0 weeks after a preceding singleton pregnancy birth at 37+0 to 41+6 weeks. Methods Multivariate logistic regression analysis of association between twin PTB and a previous spontaneous singleton early‐term birth. Main outcome measures Twin PTB rate before 37, 34 and 32 weeks of gestation. Results Among 618 twin pregnancies, 270 were born preterm, 92 of them with a preceding spontaneous singleton early‐term birth. The univariate analysis showed a significantly higher risk of twin PTB before 37, 34 and 32 weeks among those 92 women compared with those with a full‐ or late‐term birth in their previous singleton pregnancy. This association remained significant after logistic regression (odds ratio [OR] between 2.42 and 3.88). The secondary analysis, restricted to the twin pregnancies with spontaneous PTB found similar results, with a risk of PTB before 37, 34 and 32 weeks significantly higher among women with a previous spontaneous singleton early‐term birth, including after logistic regression analysis (OR between 3.51 and 3.56). Conclusion A preceding spontaneous singleton early‐term birth is a strong and easily identified risk factor for PTB in twin pregnancies. Tweetable abstract Spontaneous ‘early‐term’ birth of a singleton is a significant risk factor for future preterm births in twin pregnancies.