Higher live birth rates are associated with a normal body mass index in preimplantation genetic testing for aneuploidy frozen embryo transfer cycles: a Society for Assisted Reproductive Technology Clinic Outcome Reporting System study

Objective: To determine whether body mass index (BMI) was associated with live birth in patients undergoing transfer of frozen-thawed preimplantation genetic testing for aneuploidy (PGT-A) embryos. Design: Retrospective cohort study of cycles reported to the Society for Assisted Reproductive Technology Clinic Outcome Reporting System. Subjects: All autologous and donor recipient PGT-A–tested cycles reported to the Society for Assisted Reproductive Technology Clinic Outcome Reporting System from 2014 to 2017. Intervention(s): Body mass index. Main Outcome Measure(s): The primary outcome measure was the live birth rate, and the secondary outcome measures were the clinical pregnancy and biochemical pregnancy rates. Multivariable generalized additive mixed models and log-binomial models were used to model the relationship between BMI and outcome measures. Result(s): A total of 77,018 PGT-A cycles from 55,888 patients were analyzed. Of these cycles, 70,752 were autologous, and 6,266 were donor recipient. In autologous cycles, a statistically significant and clear nonlinear relationship was observed between the BMI and live birth rates, with the highest birth rates observed for the BMI range of 23–24.99 kg/m². When using 23–24.99 kg/m² as the referent, other BMI ranges demonstrated a lower probability of live birth and clinical pregnancy that continued to decrease as the BMI moved further from the reference value. Patients with a BMI of <18.5 kg/m² had a 11% lower probability of live birth, whereas those with a BMI of ≥40 kg/m² had a 27% lower probability than the referent. Conclusion(s): A normal-weight BMI range of 23–24.99 kg/m² was associated with the highest probability of clinical pregnancy and live birth after a frozen-thawed PGT-A–tested blastocyst transfer in both autologous and donor recipient cycles. A BMI outside the range of 23–24.99 kg/m² is likely associated with a malfunction in the implantation process, which is presumed to be related to a uterine factor and not an oocyte factor, as both autologous and donor recipient cycle outcomes were associated similarly with the BMI of the intended parent.