An Unrecognized High Incidence of Asymptomatic Uterine Torsion in Pregnancies with Adenomyosis that Complicate Cesarean Delivery

The association between adenomyosis and uterine torsion, a rare, serious obstetric condition, remains unclear and has not been systematically investigated. This study aimed to elucidate the incidence, risk factors, and clinical characteristics of uterine torsion in pregnancies complicated by adenomyosis. We conducted a retrospective cohort study of women with adenomyosis undergoing cesarean section at The University of Tokyo Hospital from 2010 to 2023. Adenomyosis was diagnosed via magnetic resonance imaging and/or ultrasonography before and/or during early pregnancy. Uterine torsion was defined as > 45° rotation around the long uterine axis during cesarean section. We compared the clinical characteristics, adenomyotic features and surgical details of women with and without uterine torsion. Among 135 pregnant women with adenomyosis, 70 underwent cesarean section. Within this cesarean delivery cohort, uterine torsion was identified in six (8.6%) women. All torsion cases were asymptomatic and involved focal type adenomyosis; these six cases represented 13.6% (6/44) of the 44 women with focal type adenomyosis in this cesarean cohort. The torsion group required 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 = 0.006) significantly more often. This study highlights a high incidence (8.6%) of asymptomatic uterine torsion in a cohort of women with adenomyosis undergoing cesarean delivery. These findings suggest that focal adenomyosis may be a key risk factor and generate an important hypothesis that requires further investigation. Surgical planning should consider the possibility of uterine torsion, which may require tailored intraoperative strategies involving non-standard incisions.