Effect of body mass index on ovarian reserve and ART outcomes in infertile women: a large retrospective study.

Background: Obesity poses a significant global health challenge, with profound implications for women's reproductive health. The relationship between ovarian reserve and body mass index (BMI) remains a subject of debate. While obesity is generally associated with poorer outcomes in assisted reproductive technology (ART), the evidence remains inconclusive. This study aimed to investigate the effect of pre-pregnancy BMI on ovarian reserve and ART outcomes in infertile patients.

Methods: We conducted a retrospective cohort study involving women who underwent in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) procedures at Tongji Hospital between 2016 and 2023. The study included 30,746 initial fresh cycles and 5,721 singleton deliveries. Patients were stratified by age and further categorized into four BMI groups: lean (< 18.5 kg/m²), normal weight (18.5-24.9 kg/m²), overweight (25.0-29.9 kg/m²), and obese (≥ 30.0 kg/m²). The primary endpoints of the study were pregnancy and perinatal outcomes. To explore the association between BMI and these outcomes, we adjusted for relevant confounding factors and utilized multivariate linear regression models, complemented by multifactorial logistic regression analyses.

Results: Anti-Müllerian hormone (AMH) levels were significantly lower in the overweight and obese groups compared to the normal weight group. After adjusting for age, a negative correlation was found between AMH and BMI in the age subgroups of 20-30 and 30-35 years. Among women aged 20-35 years, those in the overweight and obese groups had significantly fewer retrieved oocytes, mature oocytes, and two-pronuclear (2PN) embryos than their normal weight counterparts. Despite these differences, pregnancy outcomes in the overweight and obese groups were comparable to those in the normal weight group across all age categories. Additionally, obesity was linked to an increased risk of gestational diabetes mellitus, hypertensive disorders of pregnancy, and macrosomia.

Conclusions: An age-related decrease in AMH levels was evident with increasing BMI. Although being overweight or obese is associated with poorer embryo and perinatal outcomes, it does not seem to have a substantial impact on fertility.