Unexpectedly High Incidence of Asymptomatic Uterine Torsion in Pregnancies with Adenomyosis That Complicate Caesarean Delivery: A Retrospective Cohort Study

Objective: To elucidate the incidence, risk factors, and clinical characteristics of uterine torsion in pregnancies complicated by adenomyosis, which remains unstudied to date. Design: Retrospective cohort study. Setting: University Hospital Tertiary Perinatal Centre Population: Pregnant women with adenomyosis who underwent caesarean section at our institution. Methods: Adenomyosis was diagnosed via magnetic resonance imaging and/or transvaginal ultrasonography before and/or during early pregnancy. Uterine torsion was defined as >45° rotation around the uterine long axis during a caesarean section. We compared the clinical characteristics, adenomyotic features (extent, location, and size), and surgical details of women with and without uterine torsion. Main Outcome Measures: Incidence of uterine torsion, its association with adenomyosis lesion characteristics, and its impact on surgical procedures. Results: Uterine torsion was identified in 6 of 70 women (8.6%) with adenomyosis, all asymptomatic. All torsion cases involved focal-type adenomyosis, representing 13.6% (6/44) of such cases. The torsion group required significantly more supraumbilical skin incisions (50.0% [3/6] vs. 0% [0/64], P<0.001) and atypical uterine incisions (83.3% [5/6] vs. 23.4% [15/64], P=0.0062) compared to the non-torsion group. Conclusions: Asymptomatic uterine torsion has a notably high incidence (8.6%) in pregnant women with adenomyosis undergoing caesarean section, with focal-type adenomyosis emerging as a potential key risk factor. Torsion significantly complicates caesarean delivery, often necessitating non-standard surgical approaches. Consequently, in pregnancies complicated by adenomyosis, preoperative assessments and intraoperative strategies that take uterine torsion into account are crucial.