Ridout AE, Ibeto LA, Ross GN, et al. - The rate of spontaneous preterm birth in each type of congenital uterine anomaly was determined. In addition, the performance of quantitative fetal fibronectin and cervical length measurement by transvaginal ultrasound in asymptomatic women with congenital uterine anomalies for the prediction of spontaneous preterm birth at < 34 and < 37 weeks of gestation was assessed. From 4 tertiary referral centers in the United Kingdom (2001–2016), researchers assessed 319 women as having congenital uterine anomalies asymptomatic for spontaneous preterm birth. Among these women, spontaneous delivery occurred at < 34 weeks’ gestation in 7% (23/319) and at < 37 weeks’ gestation in 18% (56/319). By type, following rates of spontaneous preterm birth were reported: 26% (7/27) for unicornuate, 21% (7/34) for didelphic, 16% (31/189) for bicornuate, 13% (7/56) for septate, and 31% (4/13) for arcuate. Observations support the utility of the commonly used markers, cervical length, and quantitative fetal fibronectin, in prediction of spontaneous preterm birth in resorption congenital uterine defects but not in fusion defects. This is contrary to findings in other high-risk populations. They suggest considering these findings while planning antenatal care, and potential implications of these findings for predictive tests used in spontaneous preterm birth surveillance and intervention.