P-358 Impact of localization of diffuse adenomyosis on reproductive outcomes and pregnancy complications: A prospective cohort study of 585 patients after frozen embryo replacement cycle

Abstract Study question Does localization of diffuse adenomyosis impact reproductive outcomes after the frozen embryo transfer (FET)? Summary answer Diffuse adenomyotic lesions involving the junctional zone (JZ) have a greater negative impact on reproductive outcomes than diffuse adenomyosis of the outer myometrium (OM). What is known already Adenomyosis is associated with higher miscarriage rate, significantly lower live-birth (LB) rate, and increased risk for pregnancy-related complications. However, the impact of adenomyosis on IVF outcomes remains unclear. Adenomyosis is often treated as a homogenous disease and studies on the effects of different types of adenomyosis on reproductive outcomes have yielded inconsistent results, due to a lack of standardized diagnostic criteria and a lack of agreement on the phenotypic classification of the disease based on their severity or location. There is a lack of studies considering the effects of the severity or location of adenomyosis on reproductive outcomes after FET. Study design, size, duration This prospective cohort study was conducted at a tertiary-care hospital between January 2019 and December 2022. A total of 585 infertile women undergoing the first FET cycle were recruited. The study population included 368 women with diffuse adenomyosis where 201 women had diffuse adenomyosis of JZ and, 167 women had diffuse adenomyosis of OM. 217 women with male infertility were taken as controls. Participants/materials, setting, methods Adenomyosis was diagnosed with 2D-TVS using MUSA criteria where patients with two or more features and diffuse adenomyosis were included. Patients with diffuse adenomyosis were further divided based on the localization of adenomyotic lesions in OM or JZ. All the patients underwent FET-cycle. Pregnancy outcomes and complications were compared between different groups-those with diffuse adenomyosis of JZ, those with diffuse adenomyosis of OM, and controls. Adenomyosis patients as one group were also compared with controls. Main results and the role of chance The pregnancy rate was significantly lower in women with diffuse adenomyosis of JZ (26.37%) compared to diffuse adenomyosis of OM (47.9%) (OR:0.39, 95% CI 0.25-0.60; P