P-302 How adenomyosis changes throughout pregnancy

Abstract Study question How do the ultrasound characteristics of adenomyosis modify during pregnancy? Summary answer Signs of adenomyosis are visible in pregnancy and progressively disappear through gestation; adenomyosis was associated with an increased risk of miscarriage in the 1st trimester. What is known already Women with uterine adenomyosis may be asymptomatic (35%) or report menorrhagia (50%), dysmenorrhea (30%) and metrorrhagia (20%). Several authors recently linked this condition to subfertility since many women with “unexplained infertility” were found to have adenomyosis. Being relatively inexpensive and accurate, ultrasound is now considered the imaging modality of choice for diagnosing adenomyosis. Although the increasing interest towards the adenomyosis there are no data on the identification of sign of adenomyosis among pregnant women and evaluating their changes throughout the pregnancy. Study design, size, duration This is a retrospective exploratory cohort study conducted between 2016 and 2020 including 254 women of which 66 were diagnosed as having focal or diffuse adenomyosis (according to the MUSA classification) before conception or during the 1st trimester of pregnancy. The remaining 188 women were used as controls. Participants/materials, setting, methods Women were included if they had at least one pre-conceptional transvaginal ultrasound scan documenting adenomyosis, at least one scan per trimester and known maternal and neonatal outcomes. Diagnosis of adenomyosis was based on the MUSA classification and the recent consensus classification system for adenomyosis. We evaluated if the signs of adenomyosis were visible later in pregnancy and post-partum. Obstetric and neonatal outcomes were compared between women with or without these signs. Main results and the role of chance The globular aspect of the uterus was reported in 79% women with adenomyosis in the 1st trimester: it progressively disappeared, being present in only 38% and 2% women in the 2nd and 3rd trimester respectively and again visible in the post-partum in 65% women. Asymmetrical thickening (30%) and cysts (23%) were reported in the 1st trimester and disappeared during pregnancy. Adenomyosis was associated with miscarriage (OR 5.9 95%CI 2.4-14.9, p < 0.001) also when considering only normal conception (OR 5.1 95%CI 1.8-14.2, p = 0.002) or when correcting for maternal age (aOR 5.9, CI95% 2.3-15.2, p < 0.001). Gestational age at delivery was lower in women with adenomyosis (p = 0.004); Caesarean Sections (CS) rate was higher than in controls (OR 2.5, CI95% 1.3-4.8, p = 0.007) and this was confirmed (OR 2.4 CI95% 1.1-5, p = 0.02) also excluding women with previous CS. Limitations, reasons for caution These findings are from a monocentric retrospective study including only patients with known obstetric outcomes diagnosed with adenomyosis. Analysis was not stratified according to the mode of conception because of the small sample size, possibly introducing a bias in pregnancy outcomes. Wider implications of the findings Despite their progressive disappearance, signs of adenomyosis can be clinically relevant since associated with an increased risk of miscarriage in the first trimester also when considering only women with normal conception. Adenomyosis per se might have an influence on endometrial molecular expression resulting in impaired implantation and early development. Trial registration number not applicable