L26/P-327 Serum progesterone at frozen embryo transfer in endometriosis and adenomyosis: prospective data and integrative analysis including the Bourdon cohort

Abstract Study question Are serum progesterone levels on the day of frozen embryo transfer different in women with endometriosis or adenomyosis compared with controls, based on prospective and pooled data? Summary answer Overall progesterone levels were similar; integrative analysis with Bourdon et al.(Hum Reprod. 2024 Aug 1;39(8):1692–1700) confirmed comparable values, except lower levels in non-pregnant adenomyosis patients. What is known already Adequate progesterone exposure during frozen embryo transfer (FET) is crucial for endometrial receptivity, and low serum progesterone has been associated with reduced live birth rates in hormonally prepared cycles. Endometriosis and adenomyosis are characterized by chronic inflammation, altered steroid signaling and progesterone resistance, potentially affecting implantation. Whether affected women require higher progesterone supplementation remains controversial. Recent work by Bourdon et al. reported no differences in progesterone levels between affected patients and controls, highlighting the need for further prospective data and pooled analyses. Study design, size, duration Single-center prospective case–control study conducted between June 2020 and December 2023, including 1,927 women undergoing first single blastocyst FET, combined with an integrative analysis incorporating data from Bourdon et al. Participants/materials, setting, methods Women with ultrasound- or surgery-confirmed endometriosis or adenomyosis and unaffected controls undergoing medicated or spontaneous modified FET cycles were included. Serum progesterone was measured on the day of embryo transfer. Outcomes were analyzed by diagnosis, cycle type and reproductive outcome. Random-effects integrative analyses were performed focusing on medicated cycles to ensure methodological consistency with Bourdon et al. Main results and the role of chance Live birth rates were similar among women with endometriosis (32.1%), adenomyosis (32.3%) and controls (31.8%). In medicated cycles, serum progesterone levels on the day of FET did not differ between women with endometriosis or adenomyosis and controls, irrespective of pregnancy outcome. Integrative analysis including the Bourdon cohort confirmed no significant differences in progesterone levels between affected women and controls among those achieving live birth (endometriosis: p = 0.55; adenomyosis: p = 0.84). Among women who did not conceive, pooled analysis revealed significantly lower progesterone levels in adenomyosis compared with controls (p = 0.03), with stronger significance in diffuse adenomyosis (p = 0.02). No corresponding effect was observed in endometriosis. Within the prospective cohort, women with adenomyosis who achieved live birth had higher progesterone levels than non-pregnant women (p = 0.022), although this difference was attenuated after integrative analysis. Body mass index was the main independent determinant of progesterone levels. Overall findings suggest a condition-specific effect in adenomyosis, supported by pooled evidence. Limitations, reasons for caution Subgroup analyses were limited by sample size. Serum progesterone may not accurately reflect endometrial exposure. Integrative analysis included a single external cohort, limiting generalizability. Wider implications of the findings Integration with Bourdon et al. strengthens evidence against routine progesterone escalation in endometriosis, while adenomyosis—particularly diffuse disease—may require individualized luteal phase support. Trial registration number No