As the number of women who postpone their first pregnancy until their late 30s or early 40s is increasing, adenomyosis is more frequently encountered by obstetricians. Some studies have reported on the relationship between adenomyosis and pregnancy complications. We aimed to investigate the effect of adenomyosis on pregnancy complications and outcomes and associations between adenomyosis type and pregnancy outcomes. This multicenter retrospective 1:4 case-control study included 61 women with singleton pregnancies diagnosed with adenomyosis. The control group included women with singleton pregnancies without adenomyosis; these women were matched to those with adenomyosis using propensity scores. The incidence of obstetric complications, delivery, and neonatal outcomes were compared. The adenomyosis group (n = 61) had significantly higher incidence of preterm delivery (21.3% vs. 9.4%), hypertensive disorders of pregnancy (13.1% vs. 5.3%), cesarean delivery (46.0% vs. 20.9%), and postpartum hemorrhage (57.3% vs. 36.8%) than the control group (n = 244). Subgroup analysis by the adenomyosis type revealed that the diffuse adenomyosis group (n = 41) was significantly more likely to experience preterm labor (29.3% vs. 7.3%), hypertensive disorders of pregnancy (17.0% vs. 5.5%), severe hypertensive disorders of pregnancy (12.2% vs. 1.8%), preterm premature rupture of membranes (12.2% vs. 2.4%), cesarean delivery (61.3% vs. 18.9%), and postpartum hemorrhage (70.7% vs. 44.5%) than the control group (n = 164). The focal adenomyosis (n = 20) group was not statistically different from the control group (n = 80) with respect to obstetric complications. Women with diffuse adenomyosis require more careful perinatal management than previously thought.