Body mass index and its association with ovarian primordial follicle number

Abstract

OBJECTIVE: Previous studies have investigated the impact of body-mass index (BMI) on the ovarian reserve by correlating the BMI with the age of spontaneous menopause or outcomes in the assisted reproductive technologies. Although occasionally in agreement, many of these studies have reported contradictory findings. The purpose of this investigation was to determine the relationship between BMI and the ovarian primordial follicle (PF) number. DESIGN: Prospective study, university setting. MATERIALS AND METHODS: Normal ovaries were collected from 96 women (age 20-52 years) undergoing oophorectomy, organ donation, or autopsy. Height and weight were recorded for calculation of BMI. A single ovary was selected for determination of the total ovarian PF number utilizing a validated fractionator/optical disector method. Comparisons of log-transformed PF number between age groups (“younger”, 30-40 years old, n = 36; and “older”, 41-52 years old, n = 60) and weight groups (“normal”, BMI 18.5-24.9 kg/m2; and “overweight or obese”, BMI ≥ 25 kg/m2) were performed with the Mann-Whitney U test and two-way analysis of variance as appropriate. A p-value of < 0.05 was considered statistically significant. RESULTS: Overweight and obese subjects had lower ovarian PF counts than did normal weight subjects (p = 0.0006). After controlling for the effects of age with a two-way analysis of variance with both age group and weight group as independent variables, the overweight and obese subjects had lower PF counts than did normal weight subjects (p < 0.0001 for age group, p = 0.033 for weight group). Within age categories, the ages of subjects between the “normal” and “overweight or obese” groups were not significantly different. CONCLUSION: In this investigation, an elevated BMI was associated with lower ovarian PF number. Additional studies are needed address the relationship between BMI and the ovarian reserve.