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.