Serum progesterone concentrations on fresh blastocyst transfer day do not correlate with live birth rates

Does serum progesterone concentration on the day of single fresh blastocyst transfer relate to live birth rate (LBR)?

A retrospective single-centre cohort study was conducted at a tertiary fertility unit, involving 508 fresh single-blastocyst transfer cycles with autologous oocytes between June 2022 and August 2023. Ovarian stimulation was performed in 423 participants using a gonadotrophin-releasing hormone antagonist protocol, followed by micronized vaginal progesterone (MVP) 800 mg twice daily for luteal support starting the day after oocyte retrieval. Serum progesterone was measured on the day of transfer. The primary outcome was LBR; secondary outcomes included positive β-human chorionic gonadotrophin (β-HCG) concentration, ongoing pregnancy rate and early pregnancy loss. Data were stratified using 27 and 40 ng/ml progesterone concentration cut-offs. Non-linear associations were assessed using penalized smooth terms.

After accounting for confounding factors no association was identified between progesterone concentrations on the day of transfer and LBR. LBR showed no significant difference between individuals with serum progesterone cut-off concentrations of either 27 or 40 ng/ml (adjusted odds ratio [aOR] 0.83, 95% CI 0.13-5.31, P = 0.848 and aOR 0.94, 95% CI 0.30-2.95, P = 0.912, respectively). Progesterone over 40 ng/ml was associated with higher odds of a positive β-HCG (aOR 2.28, 95% CI 1.20-4.34, P = 0.012). Further analysis revealed that non-linear terms were unnecessary.

The data suggest that measuring progesterone concentrations on the day of a single-blastocyst transfer with MVP luteal phase support may not be indicative of LBR. This raises questions regarding the need for routine progesterone measurements and the development of rescue strategies.