O-268 Presence of adenomyosis impairs clinical outcomes in women undergoing frozen embryo transfer

Abstract Study question Does the presence of adenomyosis impact the clinical outcomes of patients undergoing frozen embryo transfer (FET)? Summary answer Presence of adenomyosis is associated with higher miscarriage and lower clinical pregnancy and live birth rates. GnRH agonist pre-treatment does not increase clinical outcomes. What is known already Presence of adenomyosis among pregnant patients has been associated with a higher incidence of miscarriage and pregnancy complications. Although the role of adenomyosis in women undergoing in vitro fertilization (IVF) has been investigated in several studies demonstrating a potential detrimental effect on live birth rates following IVF, most of them were small studies in which adenomyosis diagnosis was not confirmed based on solid ultrasonographic criteria. Considering the fragmented evidence up to date, we decided to perform a large retrospective study including women with adenomyosis undergoing FET which has been confirmed based on solid ultrasonographic criteria. Study design, size, duration Retrospective cohort study of 3503 patients undergoing their first cycle of blastocyst frozen transfer in a university-affiliated fertility center between January 2017 and December 2021. Participants/materials, setting, methods Overall, 3503 patients undergoing their first blastocyst frozen transfer through a hormonal replacement (HRT) FET cycle. Patients were categorized as adenomyosis when fulfilling to the Morphological Uterus Sonographic Assessment (MUSA) criteria and as non-adenomyosis when no-adenomyosis was identified. Among them 140 women had a confirmed diagnosis of adenomyosis based on MUSA criteria. Clinical information was retrospectively collected from medical records. Main results and the role of chance Comparisons between adenomyosis and non-adenomyosis groups revealed similar baseline characteristics in terms of patients’ weight, parity, smoking status, and age. Similarly, endometrial thickness and mean serum progesterone levels the day before FET as well as the number of embryos transferred were comparable between groups. Adenomyosis patients were more likely to proceed with a deferred FET (freeze-all protocol) as compared with no-adenomyosis women (p = 0.002) and were significantly more likely to be treated with GnRH agonist pre-treatment (2 injections) (P < 0.001). Multivariable logistic regression, adjusting for age, autologous or donor oocytes, PGT-A, deferred FET, serum progesterone levels the day before FET, GnRH agonist pre-treatment, number of embryos transferred, and adenomyosis, demonstrated that the use of GnRH agonist protocol did not affect miscarriage, clinical pregnancy rate or live birth rate. However, the presence of adenomyosis significantly decreased clinical pregnancy rates (OR 0.62, 95% CI: 0.39-0.98, P = 0.040) and live birth rates (OR 0.46, 95% CI: 0.27-0.75, P = 0.003) and significantly increased miscarriage rates (OR 2.13, 95% CI 0.98-4.37, p = 0.045). PGT-A was the only factor associated with a significative reduction in miscarriage rate. Limitations, reasons for caution The main limitation of this study is the single-center retrospective approach. Furthermore, due to the limited number of cases with adenomyosis focal and diffuse adenomyosis were analyzed together although this may be clinically distinct entities. Wider implications of the findings The results of this study demonstrate that presence of adenomyosis has significant negative impact on the clinical outcomes of patients undergoing FET. Future prospective studies are needed to create a consensus on the optimal ET technique for these patients. Trial registration number Not Applicable