Male obesity impairs early embryonic development and increases miscarriage risk in oocyte donation cycles

To evaluate the impact of male body mass index (BMI) on preimplantation development and clinical outcomes in oocyte donation cycles.

Retrospective cohort study.

A total of 7,846 embryos from 1,398 oocyte donation intracytoplasmic sperm injection cycles were analyzed. Cycles utilized fresh (n = 904) or cryopreserved (n = 494), partner (n = 1,133) or donor sperm (n = 265). Cycles involving severe male factor or preimplantation genetic testing were excluded.

Male BMI (kg/m²) at cycle start, categorized as normal weight (BMI<24.9, n = 699), overweight (BMI = 25.0-29.9, n = 561), or obese (BMI≥30, n = 138).

The primary outcome focused on the timing of preimplantation developmental milestones assessed through morphokinetics. Secondary outcomes included embryo quality, fertilization, blastocyst, implantation, miscarriage, and live birth rates. Outcomes of the first fresh (n = 1,110) or frozen (n = 106), cleavage (n = 366) or blastocyst stage (n = 850) transfer were included, comprising 1,001 single and 215 double embryo transfers. Univariate analyses and logistic regression were used to evaluate associations between BMI, embryo morphokinetics, and clinical outcomes.

Embryos from obese males showed delayed cleavage-stage development (t2, t3, t4, and t5) and reduced odds of a good-quality inner cell mass in blastocysts, compared with those from normal weight males (odds ratio = 0.80; 95% confidence interval = 0.64-0.99). Fertilization (normal weight: 75.1%, overweight: 74.6%, obese: 73.1%) and blastocyst rates (normal weight: 65.1%, overweight: 63.6%, obese: 63.8%) were comparable among the BMI groups. Implantation (normal weight: 64.8%, overweight: 64.3%, obese: 58.7%) and clinical pregnancy rates (normal weight: 60.0%, overweight: 58.9%, obese: 52.9%) were also similar. However, miscarriage rates were significantly higher among couples with obese males (13.5%) compared with those with normal weight males (9.5%) (odds ratio = 1.67; 95% confidence interval = 1.27-2.19). Although not statistically significant, live birth rates followed a similar trend (normal weight: 46.7%, overweight: 43.7%, obese: 36.5%).

Male obesity impairs early embryonic development and increases miscarriage rates, identifying male BMI as a potential risk factor in oocyte donation cycles.