Arcuate uterus does not impact the success of infertility treatments, but there is no consensus on whether it influences perinatal outcomes. The objective of the present study was to investigate whether minor congenital uterine anomalies such as an arcuate uterus contribute to perinatal complications. This was a retrospective cohort study at a single institution. The study included 1097 deliveries after 22 weeks of gestation. Transvaginal ultrasound, with three-dimensional functionality, assessed uterine morphology based on American Society for Reproductive Medicine criteria. We compared maternal backgrounds and perinatal complications between arcuate uterus and normal uterus groups. Statistical analyses, including multivariate analysis, aimed to identify independent risk factors. A total of 69 patients (7.5%) with diagnosed arcuate uterus were included. Maternal background factors showed no significant differences between groups. In perinatal complications, an arcuate uterus was associated with a significantly higher incidence of preterm delivery (13% versus 4.7%, P = 0.01), preterm premature rupture of membranes (7.2% versus 1.6%, P = 0.01), fetal growth restriction (FGR
16% versus 6.7%, P = 0.01), and abnormal placental cord insertion (33% versus 7.6%, P <
0.01). After multivariate analysis, arcuate uterus emerged as an independent risk factor for preterm delivery (adjusted odds ratio [aOR], 4.0 [95% confidence interval (CI), 1.6-9.9], P <
0.01), FGR (aOR, 2.6 [95% CI, 1.2-5.6], P = 0.02), and abnormal placental cord insertion (aOR, 6.0 [95% CI, 3.4-10.6], P <
0.01). Arcuate uterus stands as an independent risk factor for preterm delivery, FGR, and abnormal placental cord insertion. The findings emphasize the importance of recognizing even minor uterine morphological abnormalities in assessing and managing perinatal complications.