Serum progesterone level in luteal phase improves pregnancy rate in fresh cycles with blastocyst embryo transfer

OBJECTIVE: To assess the association between serum level of progesterone during stimulation and in the luteal phase with pregnancy rate in a cohort of patients undergoing in vitro fertilization and embryo transfer (IVF-ET) on day 5. METHODS: Retrospective Cohort Study. Patients: 62 infertile women, aged 24-42 years, undergoing ART at our center from May 2019 to May 2021. Progesterone was evaluated during ovarian stimulation on Day 2, Day 6, and Day 8 of stimulation, day of trigger (P4dhCG), and on the day of blastocyst transfer with 5 days of progesterone supplementation (P4d5+). We also calculated the difference of P4d5+ with P4dhCG. (∆P4). Then we divided the patients into two groups based on progesterone serum levels at P4d5+; <10ng/ml (Group A), ≥10ng/ml (Group B). The Student’s t-test was performed for continuous variables; Mann-Whitney’s Test and Spearman’s Test were used where appropriate for categorical variables. p<0.05 was considered statistically significant. RESULTS: There were positive correlations between βhCG positive with P4d5+ (p<0.001; Rho 0.770) and ∆P4 (p<0.001; Rho 0.703). The pregnancy rate doubled when the serum progesterone level was ≥10ng/ml on the fifth day of progesterone supplementation compared with P4<10ng/ml (44% vs. 21%, respectively). CONCLUSIONS: The pregnancy rate was positively correlated with the serum P4 level on the fifth day of progesterone supplementation and with the difference between the serum progesterone level in the Dd5+ / dhCG. A higher pregnancy rate was observed when serum progesterone level on the fifth day of progesterone supplementation was ≥10ng/ml.