Analysis of factors that increase serum progesterone levels on the day of hCG administration in gonadotropin-releasing hormone antagonist cycles

Objective: To explore the factors associated with elevated serum progesterone (P) levels on the day of hCG administration in patients undergoing controlled ovarian stimulation using a gonadotropin-releasing hormone antagonist (GnRH-A) protocol. Methods: fertilization-embryo transfer (IVF-ET) or intracytoplasmic sperm injection (ICSI) cycles performed between January 2018 and December 2023 at the Reproductive Medicine Center of the Affiliated Hospital of Jining Medical University. Patients were stratified into a normal progesterone group (NP group, serum P ≤ 1.5 ng/mL, n = 985 cycles) and a high progesterone group (HP group, serum P > 1.5 ng/mL, n = 407 cycles) according to the cutoff value of 1.5 ng/mL on hCG day. Clinical characteristics and endocrine parameters during ovarian stimulation were compared between groups. Univariate and multivariate logistic regression analyses were applied to identify independent factors related to elevated hCG-day progesterone levels. Results: The oocyte retrieval age, BMI, basal FSH (bFSH), and hCG-day serum LH levels were significantly higher in the NP group than in the HP group, whereas basal P (bP), antral follicle count, hCG-day serum E2, AMH, and total number of oocytes retrieved were significantly lower (all P < 0.05). No significant differences were observed in basal LH, basal E2, initial Gn dose, total Gn duration, or total Gn dose between groups (all P > 0.05). Univariate logistic regression showed that oocyte retrieval age, BMI, bFSH, bP, AMH, antral follicle count, hCG-day serum LH and E2 levels, and total oocytes retrieved were significantly associated with hCG-day progesterone levels (all P < 0.05). Multivariate analysis further confirmed that BMI (OR = 0.901), bP (OR = 2.100), hCG-day serum E2 (OR = 1.225), hCG-day serum LH (OR = 1.048), and total oocytes retrieved (OR = 1.143) were independent influencing factors (all P < 0.05). Conclusion: Basal progesterone, hCG-day serum E2 and LH levels, and total number of oocytes retrieved are independent risk factors for elevated progesterone levels on hCG day, whereas BMI serves as a protective factor.