OP11.02: The natural history in non‐obstructive congenital uterine anomalies: a prospective observational study in an unselected population

To assess the prevalence of non-obstructive uterine anomalies (CUA), the associations, and reproductive outcomes in an unselected population addressing the gynecology consultation. Consecutive women referred for gynecology routine/targeted exams, between January 2012 and December 2023 were included in the study. Three-dimensional transvaginal datasets were acquired. The subseptate uterus was classified as minor and major, depending on the internal cavity/septum surface ratio. We used an arbitrary cut-off value of 2.5. We excluded all cases subjected to hysteroscopic metroplasty. 11844 women were included in the study. In 313 cases the volume datasets were non-interpretable. We found 11289 (97.9%) cases with normal uterus and 242 (2.09%) cases with a congenital non-obstructive uterine anomaly, 81 being major. The most common anomalies were arcuate (52.89%), subseptate (21.9%) and unicornuate (9.09%) uterus. In the desiring pregnancy women with major CUA group, we found a significantly lower live-birth rate: 23/61 (37.7%) than 42/61 (68.85%) in the no-CUA matched 1:1 by age and body mass index group; p < 0.05. The rates of infertility, ectopic pregnancies, endometriosis, and irregular, painful, or heavy menstrual bleeding were similar between all women with non-obstructive CUA and those with a normal uterus. Preterm birth before 37 of amenorrhea was not more common in all women with CUA enrolled than in controls (21.6% vs 15%, respectively; p = 0.089). In the major CUA subgroup, the difference in PTB and recurrent pregnancy loss (RPL) was statistically significant (35.04% versus 15%; p < 0.05, respectively 1.1% vs 13%; p < 0.05). We found a lower prevalence of non-obstructive CUA than previously reported in an unselected population. Major CUA is an independent risk factor for lower live-birth rate, PTB and RPL. More studies in unselected populations are required.