Adverse effects of maternal and paternal body mass index on assisted reproductive techniques outcomes: A time-lapse study

OBJECTIVE: While obesity has been associated with poor reproductive outcomes, the specific factors affecting gametes remain unclear. Our primary objective was to assess the relationship between a couple's pre-pregnancy body mass index (BMI), the morphokinetic characteristics of embryos, and their potential for implantation. We analyzed standard semen parameters, sperm chromatin integrity, and oxidative stress levels in men undergoing assisted reproductive techniques (ART). METHODS: A total of 1,320 couples were categorized into nine different weight classes. Following the incubation of embryos in a time-lapse device, we evaluated embryo development and ART outcomes. RESULTS: Significant differences were observed in the percentage of sperm with normal morphology, as well as in the levels of reactive oxygen species, malondialdehyde, and total antioxidant capacity, between overweight and normal-weight men. Overweight men also showed a higher percentage of motile spermatozoa with altered chromatin. After adjusting for parental age and infertility causes, t5 and t8 durations were longer in obese women. In overweight men, t2 and t8 were delayed compared to those in normal-weight couples. Additionally, overweight couples experienced faster time of pronuclei appearance and time of pronuclei fading, along with longer t2, t5, and t8, compared to their normal-weight counterparts. Moreover, overweight males exhibited a lower fertility rate than normal-weight men. Overweight couples also demonstrated significantly lower rates of clinical pregnancy and fertilization, which correlated with higher miscarriage rates. CONCLUSION: This time-lapse study revealed that the combined pre-pregnancy BMI of parents is associated with slower pre-implantation embryo development.