Objective To clarify the clinical characteristics of pain developing in adenomyosis lesions during pregnancy and the perinatal outcomes associated with this phenomenon. Study Design Retrospective cohort study. Setting A tertiary hospital in Japan. Patients and methods Ninety one singleton pregnancies with adenomyosis who delivered between 2011 and 2021 were retrospectively analyzed. Pain during pregnancy was defined as persistent pain at the adenomyosis site with analgesics administration, and its association with perinatal outcomes was analyzed. Main outcome measures Pain at the adenomyosis lesion and its onset and duration, maximum C-reactive protein level during pain, and perinatal outcomes such as preterm delivery, preeclampsia, and blood loss. Results Among 91 singleton pregnancies with adenomyosis, 12 pregnancies (13.2%) presented with pain at the adenomyosis site. In total, 5 of the 12 pregnancies (41.7%) developed preeclampsia, which resulted in preterm delivery. The incidence of preeclampsia and preterm delivery was higher in those who experienced pain than in those without (41.7% vs. 13.9%; p<0.05, and 66.7% vs. 31.7%; p<0.05, respectively). Among women with pain during pregnancy, the maximum C-reactive protein level was significantly higher in women who developed preeclampsia than in those without (5.45 vs. 0.12 mg/dL, p<0.05). Conclusion Adenomyosis can cause pain in over one of eight pregnancies with adenomyosis, which may be associated with the increased incidence of preeclampsia resulting in preterm delivery. Women with pain at the adenomyosis lesion, especially those with high C-reactive protein levels, may be at high risk for the future development of preeclampsia.
