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

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.