[Impact of pre-pregnancy BMI on the cumulative live birth rate and perinatal outcomes in patients with PCOS undergoing first IVF/ICSI].

Objective: To investigate the effect of pre-pregnancy body mass index (BMI) on the cumulative live birth rate (CLBR) and perinatal outcomes in women with polycystic ovary syndrome (PCOS) undergoing first in vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI). Methods: The clinical data of 1 013 patients with PCOS who received first IVF/ICSI treatment in Reproductive Medicine Center, Henan Provincial People's Hospital from January 2017 to June 2020 were retrospectively analyzed. According to BMI China standard, they were divided into: normal weight group (18.5≤BMI<24.0 kg/m², 388 cases), overweight group (24.0≤BMI<28.0 kg/m², 367 cases), obese group (BMI≥28.0 kg/m², 258 cases). The effect of BMI on CLBR was analyzed by univariate analysis, multivariate logistic regression analysis and smooth curve fitting. The role of homeostasis model assessment of insulin resistance index (HOMA-IR) in the process of BMI on CLBR was analyzed by mediation analysis. Results: Among three groups, female age, basal level of follicle stimulating hormone, type of infertility and ovulation induction regimens were similar (all P>0.05). The infertility duration, basal testosterone level, HOMA-IR, the ovulation induction time and the total gonadotropin dosage increased with BMI (all P<0.01), anti-Müllerian hormone, basal luteinizing hormone level, the number of retrieved oocytes and available embryos decreased with BMI (all P<0.05). CLBR decreased with BMI increasing [84.08% (301/358) vs 74.26% (251/338) vs 71.88% (161/224); P<0.001]. The incidence of hypertensive disorder in pregnancy was highest in obese group, while premature rupture of membranes rate, premature delivery rate, low birth weight rate and macrosomia birth rate were the lowest in normal weight group. After adjusting for confounding factors, both smooth curve fitting and multiple logistic regression analysis revealed a significant trend: CLBR declined with increasing BMI (OR=0.93, 95%CI: 0.89-0.97; P=0.002), with a reduction of 41% (OR=0.59, 95%CI: 0.39-0.91; P=0.020) in overweight group, and a reduction of 48% (OR=0.52, 95%CI: 0.32-0.83; P=0.010) in obese group. HOMA-IR mediated the effect of BMI on CLBR by 27.5% (P<0.05). Conclusions: High BMI before IVF/ICSI in PCOS patients negatively impacts CLBR and raises maternal and infant risks during pregnancy and the perinatal period. 27.5% of the effect of BMI on CLBR is mediated by HOMA-IR. Thus, PCOS patients should manage their BMI and enhance insulin sensitivity prior to pregnancy.