Association analysis of body mass index on ovarian response and pregnancy outcomes during IVF / ICSI treatment: a retrospective study in Southern Han Chinese Women

Objectives The purpose of the present study is to evaluate the effect of body mass index (BMI) on cycle characteristics and in vitro fertilization / intracytoplasmic sperm injection (IVF / ICSI) outcomes of a long down-regulation protocol in Southern Han Chinese women. Methods This retrospective, observational study included 5279 infertile women undergoing IVF / ICSI cycle with a long down-regulation protocol. All the patients were divided into four subgroups by the recommended Chinese BMI cut-off points: underweight, BMI < 18.5 kg/m2; normal-weight, 18.5 kg/m2 ≤ BMI < 24.0 kg/m2; overweight, 24.0 kg/m2 ≤ BMI < 28.0 kg/m2; obese, BMI ≥ 28.0 kg/m2. The demographic data and biochemical tests of patients, the parameters related to the ovarian responsiveness to gonadotrophin stimulation, IVF / ICSI treatment characteristics and pregnancy outcomes (clinical pregnancy rate, spontaneous abortion rate and lived birth rate) were compared among BMI categories. Results The overweight and obese infertile patients required more priming gonadotropin, total gonadotropin and longer stimulation duration, and had the lower ovarian sensitivity index (OSI), lower serum progestogen (P) and estrogen (E2) on the day of HCG administration compared with the normal-weight women (P < 0.05). The overweight and obese patients had a higher spontaneous abortion rate than women in the normal-weight (13.59% vs. 10.28%, OR = 1.40, 95% CI: 1.02 - 1,90, P = 0.036; 17.58% vs.10.28%, OR = 1.92, 95% CI: 1.09 - 3.36, P = 0.023, respectively). The overweight and obese patients seemed to have lower clinical pregnancy rate and live birth rate, but the difference was not statistically significant (P > 0.05). Conclusion This study provides new epidemiological clues that the elevated BMI might impair ovarian response to gonadotropin stimulation and increase the risk of spontaneous abortion during IVF / ICSI treatment.