Obesity adversely impacts the number and maturity of oocytes in conventional IVF not in minimal stimulation IVF

Objective: The objective of this study was to assess the relationship between BMI and oocyte number and maturity in participants who underwent minimal stimulation (mini-) or conventional IVF. Methods: Participants who underwent their first autologous cycle of either conventional (n = 219) or mini-IVF (n = 220) were divided according to their BMI to analyze IVF outcome parameters. The main outcome measure was the number of oocytes in metaphase II (MII). Secondary outcomes included the number of total oocytes retrieved, fertilized (2PN) oocytes, cleavage and blastocyst stage embryos, clinical pregnancy (CP), and live birth (LB) rates. Results: In conventional IVF, but not in mini-IVF, the number of total oocytes retrieved (14.5 +/- 0.8 versus 8.8 +/- 1.3) and MII oocytes (11.2 +/- 0.7 versus 7.1 +/- 1.1) were significantly lower in obese compared with normal BMI women. Multivariable linear regression adjusting for age, day 3 FSH, days of stimulation, and total gonadotropin dose demonstrated that BMI was an independent predictor of the number of MII oocytes in conventional IVF (p = 0.0004). Additionally, only in conventional IVF, BMI was negatively correlated with the total number of 2PN oocytes, as well as the number of cleavage stage embryos. Conclusions: Female adiposity might impair oocyte number and maturity in conventional IVF but not in mini-IVF. These data suggest that mild ovarian stimulation might yield healthier oocytes in obese women.