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.