Background: Premature progesterone elevation (PE) on the day of human chorionic gonadotropin (hCG) trigger during controlled ovarian stimulation has been reported in IVF/ICSI cycles despite the use of GnRH agonist or antagonist protocols. The impact of elevated progesterone levels on reproductive outcomes remains controversial, particularly regarding implantation and clinical pregnancy rates. Identifying clinically relevant progesterone thresholds may improve treatment strategies and optimize IVF/ICSI outcomes.

Objective: To evaluate the relationship between serum progesterone levels on the day of hCG trigger and reproductive outcomes in IVF/ICSI cycles and to determine the progesterone threshold associated with adverse clinical outcomes.

Methods: This prospective cohort study included 95 infertile women aged 20–35 years undergoing IVF/ICSI treatment at Ain Shams University Hospital between June 2023 and October 2024. Participants were categorized according to trigger-day serum progesterone levels into three groups: <1.3 ng/mL, 1.3–1.5 ng/mL, and >1.5 ng/mL. Demographic characteristics, hormonal profiles, ovarian response parameters, fertilization rate, implantation rate, and clinical pregnancy outcomes were compared. Receiver operating characteristic (ROC) analysis was performed to evaluate the predictive value of serum progesterone for pregnancy outcomes.

Results: Among the participants, 83.2% had progesterone levels <1.3 ng/mL, 4.2% had levels between 1.3 and 1.5 ng/mL, and 12.6% had levels >1.5 ng/mL. Clinical pregnancy rates were 43.0%, 50.0%, and 25.0%, respectively. Although differences in implantation and pregnancy rates did not reach statistical significance, outcomes were consistently lower in women with progesterone levels >1.5 ng/mL. No significant differences were observed in oocyte yield, embryo quality, fertilization rate, or baseline hormonal parameters. ROC analysis identified a progesterone cutoff value >0.7 ng/mL for predicting pregnancy outcomes (AUC = 0.622, sensitivity = 66.7%, specificity = 64.3%).

Conclusions: Elevated serum progesterone on the day of hCG trigger, particularly levels >1.5 ng/mL, is associated with reduced implantation and clinical pregnancy outcomes in IVF/ICSI cycles. Careful monitoring of progesterone levels and individualized treatment approaches, including consideration of freeze-all strategies, may improve reproductive success.