Impact of uterine malformations on pregnancy and neonatal outcomes of IVF/ICSI-frozen embryo transfer

STUDY QUESTION What is the impact of uterine malformations on reproductive and neonatal outcomes of IVF/ICSI-frozen embryo transfer? SUMMARY ANSWER Unification defective uteri are associated with poorer neonatal outcomes including higher preterm delivery rate and lower birthweight, and septate uteri are associated with worse fertility outcomes including higher miscarriage and lower live birth rates (LBRs). WHAT IS KNOWN ALREADY Several studies have investigated the negative effects of uterine malformations on pregnancy outcomes. However, an all-round and definitive conclusion has not been reached yet owing to the relatively low incidence of the disease and the heterogeneity of study populations, especially among women undergoing ART. STUDY DESIGN, SIZE, DURATION This was a retrospective cohort study including 411 women with congenital uterine anomalies and 14 936 women with a normal uterus who underwent first frozen-thawed embryo transfer cycles of IVF/ICSI from July 2008 to August 2019. We compared reproductive outcomes. PARTICIPANTS/MATERIALS, SETTING, METHODS Reproductive outcomes of women with uterine malformations were studied through three propensity score-matched comparisons (patients with bicorporeal uterus, septate uterus and hemi-uterus [bicorporeal, septate and hemi-uterus groups, respectively] along with corresponding control groups without uterine malformations). We also compared pregnancy and neonatal outcomes, and performed subgroup analysis addressing didelphus, bicornuate uteri and septate uteri before and after surgery independently. MAIN RESULTS AND THE ROLE OF CHANCE Compared to the matched control group, women with a bicorporeal uterus had a significantly lower LBR (24.4% versus 34.8%, odds ratio (OR) 0.61 [95% CI: 0.37, 1.00], P = 0.048). The incidence of miscarriage and preterm delivery was higher but not statistically significant (29.0% versus 18.1%, OR 1.85 [95% CI: 0.82, 4.19], P = 0.135; 22.6% versus 9.9%, OR 2.64 [95% CI: 1.07, 6.52], P = 0.063, respectively). In addition, the bicorporeal group had a significantly lower gestational age, higher caesarean rate and lower birthweight than bicorporeal control. Women with a septate uterus had comparable clinical pregnancy rates to controls (43.3% versus 49.9%, OR 0.77 [95% CI: 0.57, 1.04], P = 0.091), increased miscarriage rates (23.5% versus 13.0%, OR 2.05 [95% CI: 1.18, 3.58], P = 0.010) and lower LBRs (29.4% versus 42.2%, OR 0.57 [95% CI: 0.41, 0.79], P = 0.001). In both singleton and twins pregnancies, pregnancy and neonatal outcomes were comparable between women with a septate uterus and control. Women with a hemi-uterus had a tendency for lower clinical pregnancy rate (36.8% versus 42.3%, OR 0.80 [95% CI: 0.52, 1.21], P = 0.287) and LBR (29.8% versus 33.1%, OR 0.86 [95% CI: 0.55, 1.34], P = 0.502), compared to women without malformations. The incidences of miscarriage and preterm delivery, respectively, were 16.7% versus 16.6% (OR 1.01 [95% CI: 0.41, 2.47], P = 0.989), and 9.5% versus 11.4% (OR 0.82 [95% CI: 0.27, 2.51], P = 1) in women with a hemi-uterus as compared to control. LIMITATIONS, REASONS FOR CAUTION This was a single-centre, retrospective study in which neonatal data were extracted from parental questionnaires. The information on uteri septum type and surgery methods was poorly presented, with limited detail. In patients with uterine malformations, the number of babies with birth defects and twin pregnancies was relatively small, limiting the power of the study. WIDER IMPLICATIONS OF THE FINDINGS Compared to patients with a normal uterus, women with uterine malformation have poorer reproductive outcomes. Pregnant women with a uterine anomaly need to be managed as high-risk pregnancies and followed with appropriate obstetric review. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the National Ministry of Technology (2018YFC1003000), the Elite Team Project of Ninth People's Hospital affiliated to Shanghai Jiao Tong University School of Medicine (JY201801), Shanghai Sailing Program (21YF1423200) and the Fundamental Research Program Funding of Ninth People's Hospital affiliated to Shanghai Jiao Tong University School of Medicine (JYZZ117). B.W.M. is supported by an NHMRC Investigatorgrant (GNT1176437). B.W.M. reports consultancy (with stock options) for ObsEva. B.W.M. has received research funding from Ferring and Merck. The authors declare no other competing interests.