Prolonged Ovarian Stimulation Does Not Worsen Neonatal Outcomes After Fresh Embryo Transfers

To investigate the relationship between prolonged ovarian stimulation and neonatal outcomes after autologous fresh embryo transfer (fET). A retrospective cohort study. University-affiliated centres. 3529 patients underwent autologous in vitro fertilisation (IVF) cycles between August 1, 2016 and December 31, 2022, with a live singleton birth after fET. Univariate and multivariate regression analyses were used to determine the relationship between prolonged ovarian stimulation and neonatal outcomes. Propensity score matching (PSM) was applied to evaluate independent effects. Neonatal outcomes. Multivariate regression showed no significant association between simulation duration and birthweight (adjusted β: 4.19, 95% confidence interval [CI]: -13.86 to 22.23; p = 0.6494) or gestational age (GA) (adjusted β: -0.01, 95% [CI]: -0.09 to 0.06; p = 0.7403) Categorical analysis of neonatal outcomes, including low birthweight (LBW) (adjusted Odds Ratio [OR]: 0.94, 95% [CI]: 0.70 to 1.25; p = 0.6501), macrosomia (adjusted OR: 0.95, 95% [CI]: 0.78 to 1.16; p = 0.6294), small for gestational age (SGA) (adjusted OR: 0.95, 95% [CI]: 0.75 to 1.19; p = 0.6465), large for gestational age (LGA) (adjusted OR: 1.02, 95% [CI]: 0.85 to 1.21; p = 0.8542) and preterm (adjusted OR: 0.93, 95% [CI]: 0.77 to 1.11; p = 0.4191), revealed no associations with stimulation duration. PSM analysis confirmed these findings. Prolonged ovarian stimulation does not appear to increase adverse neonatal outcomes in singleton newborns after autologous fET.