Male adiposity impairs clinical pregnancy rate by in vitro fertilization without affecting day 3 embryo quality

Objective Male adiposity is detrimental for achieving clinical pregnancy rate (CPR) following assisted reproductive technologies (ART). The hypothesis that the association of male adiposity with decreased success following ART is mediated by worse embryo quality was tested. Design and Methods Retrospective study including 344 infertile couples undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) cycles was performed. Cycle determinants included number of oocytes retrieved, zygote PN-score, total number of embryos available on day 3, number of embryos transferred, composite day 3 grade for transferred embryos, composite day 3 grade per cycle, and CPR. Results Couples with male body mass index (BMI) over 25 kg m^-2 (overweight and obese) exhibited significantly lower CPR compared to their normal weight counterparts (46.7% vs. 32.0% respectively, P = 0.02). No significant difference was observed for any embryo quality metrics when analyzed by male BMI: mean zygote PN-scores, mean composite day 3 grades for transferred embryos or composite day 3 grades per cycle. In a multivariable logistic regression analysis adjusting for female age, female BMI, number of embryos transferred and sperm concentration, male BMI over 25 kg m^-2 was associated with a lower chance for CPR after IVF (OR = 0.17 [95% CI: 0.04-0.65]; P = 0.01) but not after ICSI cycles (OR = 0.88 [95% CI: 0.41-1.88]; P = 0.75). In this cohort, male adiposity was associated with decreased CPR following IVF but embryo quality was not affected. Conclusions Embryo grading based on conventional morphologic criteria does not explain the poorer clinical pregnancy outcomes seen in couples with overweight or obese male partner.