Serum progesterone measurement on the day of fresh embryo transfer and its correlation with pregnancy success rates: A prospective analysis

Studies regarding serum Progesterone (P4) concentration and Clinical Pregnancy Rates (CPR) in fresh Embryo Transfer (ET) after Controlled Ovarian Stimulation Cycles (COS) remain inconclusive. To find a P4 cutoff point on fresh ET day associated with higher CPR, and to identify predictive factors of CPR and P4, the authors conducted a prospective cohort of 106 patients who underwent COS at a public IVF center. The luteal phase was supported with vaginal micronized progesterone (200 mg, 8/8h), beginning on oocyte retrieval day. The primary outcome was CPR beyond the 8^th week of pregnancy. A ROC curve was constructed to identify the best cutoff point correlated with higher CPR. Multivariate analysis evaluated predictive variables of CPR and P4 concentration. P4 levels showed no significant differences between pregnant and non-pregnant patients (67.12 ± 31.1 ng/mL vs. 64.17 ± 61.76, p = 0.7465). The cutoff point correlated with higher CPR was P4 ≥ 28.9 ng/mL (AUC 0.5654). Women's age (OR = 0.878; 95 % CI 0.774-0.995) and top-quality embryo transfer (OR = 2.89; 95 % CI 1.148-7.316) were associated with CPR. Women's age ≥ 40 years (OR = 0.0956; 95 % CI 0.0156-0.5851), poor response to COS (OR = 0.0964; 95 % CI 0.0155-0.5966), and follicles ≥ 10 mm (OR = 1.465; 95 % CI 1.013-2.117) were associated with the cutoff point. As the ROC curve was unsatisfactory, P4 ≥ 28.9 ng/mL should not be used to infer gestational success. In fresh ET, P4 concentration may merely reflect a woman's age and individual response to COS rather than being a reliable CPR predictor.