Obesity Is Associated With an Increased Risk of Early Pregnancy Loss Following Euploid Frozen Embryo Transfer.

OBJECTIVE: To determine whether obesity is associated with an increased risk of pregnancy loss in patients undergoing autologous euploid frozen embryo transfer (FET). DESIGN: Retrospective cohort study. SUBJECTS: Patients with recorded body mass index (BMI) from nine clinical sites during January 2019 to December 2024 undergoing first, autologous, single, euploid FET were included. Other PGT indications were excluded. EXPOSURE: ). MAIN OUTCOME MEASURES: Primary outcome was biochemical pregnancy loss (bHCG>5mIU/ml without ultrasound evidence of pregnancy until bHCG <5mIU/ml) or clinical pregnancy loss (ultrasound evidence of at least an intrauterine gestational sac, which did not progress to live birth). Secondary outcomes included implantation, ectopic, clinical and ongoing pregnancy (8-9 weeks gestational age with cardiac activity) and live birth (neonate > 24 weeks gestational age). While there was no difference in implantation (aRR 0.98, 95% CI 0.86-1.37, p=0.09), patients with obesity had lower chances of clinical (aRR 0.96, 95% CI 0.94-0.99, p=0.002) and ongoing pregnancy (aRR 0.94, 95% CI 0.92-0.96, p<0.001) and livebirth (aRR 0.92, 95% CI 0.91-0.94, p<0.001). Risk of pregnancy loss was attenuated in parous patients with obesity (aRR 0.90, 95% CI 0.79-1.02, p=0.09). CONCLUSION: When accounting for embryonic aneuploidy in the setting of euploid only transfers, patients with obesity had a 19% increased risk of early pregnancy loss compared to non-obese patients, with risk rising across BMIs and BMI categories.