O-146 Assessment of focal and diffuse adenomyosis lesions before and after pregnancy on magnetic resonance imaging : a cohort of 139 patients

Abstract Study question How to assess the different adenomyosis phenotype before and after pregnancy on magnetic resonance imaging according to stringent validated criteria ? Summary answer Diffuse adenomyosis increases significantly after pregnancy while the rate of focal adenomyosis and the mean volume of focal adenomyosis lesions decrease significantly after pregnancy. What is known already Adenomyosis and endometriosis are benign hormone-dependent disorders associated with pelvic pain, dysmenorrhea and/or infertility. The natural course of adenomyosis and endometriosis is still unclear, particularly during pregnancy. Pregnancy is considered to have a positive impact on endometriosis. Several studies regarding the impact of adenomyosis on pregnancy are available. Adenomyosis can cause fertility disorders, miscarriage, preterm birth. However, available data evaluating the effect of pregnancy on adenomyosis are lacking. Study design, size, duration Between January 1st 2010 and September 30th 2020, 139 patients were followed in our referral care center (Gynecology department of Port-Royal Hospital, Paris) for symptomatic adenomyosis and or endometriosis. For each of them, a magnetic resonance imaging were performed before and after pregnancy. The data based on magnetic resonance imaging, pre- and post-pregnancy, were analyzed in a single retrospective study. Participants/materials, setting, methods Patients had to be over 18 years old, to be pregnant and to be followed for symptomatic adenomyosis or endometriosis without any previous surgery. Each pelvic magnetic resonance imaging were performed by a single experienced radiologist. The protocol was identical on a 1.5 T magnetic resonance imaging machine based on validated criteria. The rate of diffuse and focal adenomyosis, the volume of focal adenomyosis lesions and the thickness of maximal junctional zone were reported. Main results and the role of chance The mean age of patients was 34.6 ± 3.4 years old, 83 (59.7%) of patients underwent assisted reproductive technology to be pregnant. The mean time interval between the MRI and the delivery was 55.2 months and the mean time interval between the delivery and the MRI was 32.2 months. Before pregnancy, there was 96 (69.1%) patients with adenomyosis, all phenotype combined versus 111 (79.9%) after pregnancy (p = 0.04) on magnetic resonance imaging. The rate of diffuse adenomyosis increased significantly on magnetic resonance imaging after pregnancy compared to before pregnancy (n = 22 (15.8%) vs n = 41 (29.5%), p = 0.01). The thickness of junctional zone maximal was significantly higher after pregnancy (8.0 mm ± 5.1 vs 12.0 mm ± 4.8, p < 0.01). The rate of focal adenomyosis (n = 55 (39.6) vs n = 34 (24.5), p = 0.01) as well as the volume of focal adenomyosis lesions (6.7 mm3 2.5± vs 6.4 mm3 ± 2.3, p < 0.01) decreased significantly after pregnancy on magnetic resonance imaging. Limitations, reasons for caution This single-center study was conducted in a referral center whom patients presented more severe forms of adenomyosis, which could have affected the external validity of this study. The mean time interval between delivery and MRI was 32.2 month which implies a short follow up period to observe long term outcomes. Wider implications of the findings The hypothesis that a specific hormonal environment during pregnancy may imply a positively impact of the evolution of focal adenomyosis is raised by this study. The evolution of focal adenomyosis after pregnancy is similar to the evolution of endometriosis lesions volume that support shared etiopathogenic mechanisms between the two entities. Trial registration number ‘not applicable’