Impact of Unicornuate Uterus on Third-Trimester Obstetric Outcomes in Nulliparous Women

Background: Pregnancies in women with a unicornuate uterus are associated with an increased risk for specific adverse pregnancy and obstetric outcomes. We sought to investigate the obstetric outcomes of singleton pregnancies in nulliparous women with a unicornuate uterus in the third-trimester and to determine safe and appropriate modes of delivery. Methods: This retrospective cohort study included 94 nulliparous women with singleton pregnancies and a unicornuate uterus, along with 278 matched controls with a normally shaped uterus, from March 2009 to March 2019. Results: A total of 124 patients were diagnosed with a unicornuate uterus in the obstetrics department after the 28th week of pregnancy, including 94 nulliparous women. Compared to pregnancies with normal uterine morphology, a unicornuate uterus is associated with an increased risk of preterm delivery (PTD), preterm prelabor rupture of membranes (PPROM), malpresentation, caesarean section (CS), intrauterine growth restriction (IUGR), and neonatal intensive care unit (NICU) admission. Additionally, pregnancies with unicornuate uterus show significantly lower gestational age at delivery, as well as lower rates of term delivery and vaginal delivery. No increased risk was observed for in-labor CS rates or labor duration. In total, 17 pregnant women in the unicornuate uterus group had vaginal deliveries, including 2 who had previously undergone rudimentary horn resection. Conclusions: The presence of a unicornuate uterus is associated with an increased risk of specific adverse obstetric outcomes compared to pregnancies in women with a normal uterus. However, vaginal delivery may be considered in in women with a unicornuate uterus thorough evaluation.