Effect of body mass index on the cumulative live birth rate over multiple complete IVF cycles in women with polycystic ovary syndrome: A retrospective study

The purpose of this study was to investigate the effect of body mass index (BMI) before treatment on the cumulative live birth rate (CLBR) over multiple complete in vitro fertilization (IVF) cycles in patients with polycystic ovary syndrome (PCOS).This study is a single-center retrospective cohort study. It included 5016 patients with PCOS who started their first IVF cycle in our hospital between 2009 and 2018. Kaplan-Meier and log-rank tests were used for the comparison of CLBR across BMI groups. Univariate, multivariate models and stratification analysis were used to evaluate possible influencing factors of CLBR. Smoothing curve fitting was applied to present the correlation between BMI and CLBR. A one-line linear regression model was compared with a two-piecewise linear model using a log-likelihood ratio test.During the 8-year follow-up, 3604 women (71.85%) obtained at least one live birth. The study population was grouped according to BMI, with BMI ranging from [14.53-23.00) kg/m2 in the normal weight group, [23.00-27.50) kg/m2 in the overweight group, and [27.50-37.80] kg/m2 in the obese group, respectively. The CLBR of the obese group and the overweight group were significantly lower than the normal weight group. In the multivariate regression model, HR for CLBR was 0.86 [95%CI: 0.78-0.95] for the obese group, and 0.93 [0.86-1.00] for the overweight group, compared with the normal weight group as control. The curve fitting after adjustment for confounding factors and log-likelihood ratio test showed a one-line linear negative correlation between BMI and CLBR.We concluded that the BMI of PCOS patients had a negative one-line linear correlation with CLBR over multiple complete cycles.