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The association between obstetrical history and preterm birth in women with uterine anomalies

Abstract Objective: To estimate the association between obstetric history and preterm birth in women with uterine anomalies. Methods: This was a retrospective cohort study of women with uterine anomalies managed by one maternal–fetal medicine practice from 2005 to 2016. Women were separated into three groups based on their most recent pregnancy outcome: preterm birth <37 weeks, nulliparous, and term birth. Delivery outcomes were compared across the three groups, with the primary outcome being preterm birth <37 weeks. A subgroup analysis was performed in women with major uterine anomalies (unicornuate, bicornuate, and didelphys). Results: A total of 283 women with uterine anomalies were included. Preterm birth <37 weeks was 60.4% in women with prior preterm birth versus 18.2% in nulliparous women, versus 15.8% in women with a prior term birth (p < .001). The difference between nulliparous women and women with a prior term birth was not significant (p = .635). Among the 118 women with major uterine anomalies, the likelihood of preterm birth was also highest in the prior preterm birth group (71.4 versus 26.1 versus 25.0%, p < .001), and the difference between nulliparous women and women with a prior term birth was not significant (p = .906). Conclusions: In women with uterine abnormalities, a prior preterm birth is significantly associated with recurrent preterm birth. However, a prior term birth does not lower the risk of preterm birth as compared to nulliparous women.