Obesity as a Persistent Risk Beyond Aneuploidy

Background: Maternal obesity remains a prevalent metabolic factor that may independently impair reproductive success. Whether obesity compromises live birth and implantation rates, after controlling for euploidy embryo status, is important to determine. Objective: To evaluate the impact of body mass index (BMI) on live birth rates (LBR) and clinical miscarriage rates (MC) from preimplantation genetic testing for aneuploidy (PGT-A) tested single frozen embryo transfer (eSET) cycles. Design: Retrospective cohort study. Materials and Methods: A total 3,435 PGT-A tested eSET cycles (2023–2024) at a single private fertility center were stratified by body mass indexes underweight (<18.5), normal (18.5-24.9), overweight (25-29.9), obesity I (30-34.9), obesity II (35-39.9) and obesity III (40+). Chi-square, Fisher’s exact, Spearman correlation, and logistic regression applied (p<0.05). Results: LBR declined significantly at BMI ≥30 (47–49% vs 56–57%, p<0.001). Miscarriage increased with BMI (Spearman r=0.06, p<0.001). Not-pregnant rates were equivalent across all BMI groups (ns). BMI independently predicted LBR on multivariate analysis (OR 0.84/SD, p<0.001). Conclusions: In PGT-A tested eSET cycles, BMI ≥30 was independently associated with lower LBR and higher pregnancy loss despite confirmed euploid embryo transfer. The not-pregnant rate was equivalent across BMI categories, which could suggest obesity impairs pregnancy maintenance rather than implantation. Unlike aneuploidy, which PGT-A effectively neutralizes, obesity-related pregnancy loss continues to occur after chromosomal screening. Among pregnant cycles, loss rates were 24% in normal BMI vs 33–35% in obese patients. It is critical for discussions and pre-conception weight counseling in patients undergoing PGT-A eSET to minimize these differences.