Differences in the incidence of obstetric complications depending on the extent and location of adenomyosis lesions

Objectives Although adenomyosis is reportedly associated with adverse pregnancy outcomes, clinical factors related to the high risk of obstetric complications are unclear. This study aimed to elucidate the characteristics of adenomyosis lesions associated with the increased incidence of obstetric complications based on imaging findings. Methods This was a retrospective, observational cohort study conducted in a tertiary perinatal care center. Eighty-eight singleton pregnant women with adenomyosis were included in the study. Based on magnetic resonance imaging or ultrasonography before and/or during pregnancy, patients were classified according to three types of image characteristics: the extent of adenomyosis lesion (focal type or diffuse type), location of the lesion (extrinsic type, intrinsic type, or indeterminate type), the positional relationship between the lesion and the placenta (placenta distant from adenomyosis or placenta over adenomyosis), and the incidence of obstetric complications were examined. Results Patients with diffuse type adenomyosis are significantly more likely to have spontaneous second-trimester miscarriage (diffuse type vs. focal type: 16.7 vs. 0%, p < .01), preterm premature rupture of membranes (19.4 vs. 1.9%, p < .01), and preeclampsia (25.0 vs. 7.7%, p = .02), as compared to those with focal type adenomyosis. In a comparison of the three location types, the incidence of placental malposition was higher in patients with the extrinsic type adenomyosis (extrinsic type vs. intrinsic type vs. indeterminate type: 20.0 vs. 6.7 vs. 2.3%, p = .03). Comparisons between the types of the placenta over or distant from adenomyosis lesion displayed no significant differences in the frequencies of obstetric complications. Conclusions We demonstrated that the frequency of obstetric complications related to adenomyosis varies depending on the extent and location of the lesion; patients with diffuse type adenomyosis have an increased risk of spontaneous second-trimester miscarriage, preterm premature rupture of membranes, and preeclampsia, while patients with extrinsic type adenomyosis have an increased risk of placental malposition. Imaging evaluation of adenomyosis prior to conception or early in pregnancy may be useful for the obstetrical risk assessment among patients with adenomyosis.