O-146 Serum Progesterone levels do not differ between patients with endometriosis and unaffected patients who conceive after Hormone Replacement Therapy-Frozen Embryo Transfer (HRT-FET) cycles
Authors: Bourdon M , Maignien C , Sorel M , Guibourdenche J , Patrat C , Marcellin L , Jobin T , Chapron C , Santulli P 
Published: July 2024

Study question

Do endometriosis women who achieve a live birth (LB) after Hormone Replacement Therapy-Frozen Embryo Transfer (HRT-FET) have different transfer-day progesterone levels than controls?

Summary answer

In women achieving a LB after HRT-FET, serum progesterone levels on the day of the transfer did not differ between endometriosis and unaffected patients.

What is known already

In HRT-FET, several studies have highlighted the correlation between serum progesterone levels at the time of frozen embryo transfer and LB rates. In the pathophysiology of endometriosis, progesterone resistance is typically described in the eutopic endometrium. This has led to the hypothesis that women with endometriosis may require higher progesterone levels to achieve a LB, especially in HRT-FET cycles without a corpus luteum.

Study design, size, duration

We conducted an observational cohort study at the university-based reproductive medicine center of our institution, focusing on women who underwent a single autologous frozen blastocyst transfer after HRT using exogenous estradiol and micronized vaginal progesterone for endometrial preparation between January 2019 and December 2021. Women were included only once during the study period. Serum progesterone levels were measured on the morning of the FET by a single laboratory.

Participants/materials, setting, methods

Patients were divided into groups based on whether they had endometriosis or not and whether they achieved a LB. The diagnosis of endometriosis was based on published imaging criteria (transvaginal sonography/magnetic resonance imaging) and/or confirmed histology. The primary outcome was progesterone levels on the day of the HRT-FET leading to a LB in patients with endometriosis compared to unaffected women. Subgroup analyses were performed based on the presence of deep infiltrating endometriosis or adenomyosis.

Main results and the role of chance

A total of 1784 patients were included. The mean age of the women was 35.1 ± 4.1 years. Five hundred and sixty women had endometriosis, while 1224 did not. 179/560 (32.0%) with endometriosis and 381/1224 (31.2%) without endometriosis achieved a LB. Among women who achieved a LB after HRT-FET, there was no significant difference in the mean progesterone level on the day of the HRT-FET between those with endometriosis and those without (13.6 ± 4.3 ng/mL versus 13.2 ± 4.4 ng/mL, respectively; p = 0.302). In the subgroup of women with deep infiltrating endometriosis (n = 142) and adenomyosis (n = 100), the mean progesterone level was 13.1 ± 4.1 ng/mL and 12.6 ± 3.7 ng/mL, respectively, with no significant difference compared to endometriosis-free patients. After adjustment for BMI, parity, duration of infertility, and tobacco use, neither the presence of endometriosis (coefficient 0.38; 95% CI -0.63 to 1.40; p = 0.457) nor the presence of adenomyosis (coefficient 0.97; 95%CI -0.24 to 2.19; p = 0.114) was associated with the progesterone level on the day of HRT-FET. Among women who did not conceive, there was no significant difference in the mean progesterone level on the day of the HRT-FET between those with endometriosis and those without (p = 0.709).

Limitations, reasons for caution

The primary limitation of our study is associated with its observational design. Extrapolating our results to other laboratories or different routes and/or dosages of administering progesterone also requires validation.

Wider implications of the findings

This study shows that patients diagnosed with endometriosis do not require higher progesterone levels on the day of a frozen blastocyst transfer to achieve a LB in hormonal replacement therapy cycles.

Trial registration number

NA