Diana Polotov

Background: Does maternal body mass index (BMI) influence embryo morphokinetics in fresh embryo transfer cycles, and how does this relate to clinical outcomes and obstetric complications? Methods: A retrospective cohort study was conducted on 2238 fresh embryo transfer (ET) cycles, categorized into four BMI groups: underweight, normal weight, overweight, and obese. Baseline characteristics, stimulation parameters, hormonal profiles, morphokinetic data, and pregnancy and delivery outcomes were analyzed. Results: Higher BMI was associated with more anovulatory infertility and greater endometrial thickness. Peak estradiol and estradiol-to-oocyte ratios declined progressively with increasing BMI, despite preserved oocyte yield and embryo quality scores. Interestingly, the underweight group exhibited a significantly distinct biphasic morphokinetics developmental pattern compared with the overweight and obese groups. Pregnancy rates, including clinical and live birth, did not differ significantly across BMI groups. However, obese women had markedly higher cesarean section rates (51.9% vs. ~25–28% in other groups) and a non-significant trend toward more gestational diabetes. Other perinatal outcomes, such as preeclampsia and preterm birth, were not significantly different. Conclusions: In fresh IVF cycles, a higher BMI does not impair pregnancy achievement but is linked to altered hormonal response and increased obstetric risk, particularly cesarean delivery. These findings highlight the importance of preconception counseling and targeted obstetric management for women with elevated BMI undergoing fresh ET.

This prospective, observational study investigated the incidence of irregular cleavage (IRC) among human embryos and its influence on IVF treatment outcomes. It included 1001 women who underwent 1976 assisted reproduction treatments during 2016–2021 in a single IVF clinic. Embryo morphokinetics were analyzed and evaluated for the association between IRC and women’s characteristics, treatment characteristics, and pregnancy outcomes. The incidence of IRC was 17.5% (1689/9632 embryos). Of these, 85% of the embryos had one IRC, 15% had multiple IRC and 35% of IRC events occurred during the embryo’s first cell cycle. IRC embryos were found to correlate with male factor (p = 0.01) and higher ICSI rate (p = 0.01). Age, BMI, parity, basal FSH level, stimulation protocol, and number of retrieved oocytes did not differ between groups. Embryos with early IRC or more than one IRC had lower blastulation rates (p = 0.01 for each). Fresh cycles with IRC embryos had a lower clinical pregnancy rate (p = 0.01) and embryos with early IRC had a lower live birth rate (p = 0.04) compared to embryos without IRC. Frozen transfer cycles of blastocyst embryos, with or without IRC, had comparable results. In conclusion, the number of abnormal cleavage events and their timing are important factors in the prognosis of the developing human embryo.