Analysis of hemi-uterus pregnancy outcomes in uterine malformations: a retrospective observational study

Background The association between uterine malformations and adverse pregnancy outcomes is well recognized. However, studies on adverse pregnancy outcomes based on one kind of anatomical commonality between different uterine anomalies have not been reported. This study aimed to investigate pregnancy outcomes in pregnancies with uterine malformations when the pregnancy is confined to a hemi-uterus. Methods A retrospective observational study of 336 women who gave birth at our hospital from 2015 to 2021 was performed. Women ( n = 112) with a unicornuate, complete bicornuate, or didelphic uterus were set as the study group, and women ( n = 224) with a normal uterus were set as the reference group. Maternal and neonatal outcomes were evaluated and compared between the two groups using Student’s t-test, one-way ANOVA, Chi-squared test, Yates correction for continuity, or Fisher’s exact test. Modified Poisson regression analyses were used to estimate the relationships between the hemi-uterus pregnancy and preterm birth, preterm premature rupture of membranes, and cesarean section rates by adjusting for potential confounders. A P value < 0.05 was considered significant. Results Women in the study group had a higher history of spontaneous abortion (24.1% vs. 10.7%, P = 0.002) and intrauterine fetal death (5.4% vs. 0.4, P = 0.006). Compared with the reference group, the study group had significantly higher rates of assisted reproductive technology (9.4% vs. 2.2%, P = 0.001) and cord-around-the neck (54.5% vs. 29.9%, P = 0.000). Modified Poisson regression analyses showed that the study group was at higher risk for preterm birth (aRR, 6.8; 95% CI 2.7–16.7), preterm premature rupture of membranes (aRR, 14.1; 95% CI 3.2–62.5), malpresentation (aRR, 13.2; 95% CI 6.3–27.7), and cesarean section (aRR, 4.4; 95% CI 3.3–5.7). Conclusion Women with a unicornuate, didelphic, or complete bicornuate uterus are at higher risk for some adverse pregnancy outcomes than those with a normal uterus.