To investigate the pregnancy and obstetric outcomes of patients with congenital uterus didelphys who achieved clinical pregnancy after in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI). This was a retrospective matched-cohort study of 83 infertile patients with uterus didelphys who underwent IVF/ICSI and achieved clinical pregnancy from January 2005 to December 2018 at our center. For each patient in the study group, three control patients with normal uterine morphology who underwent IVF/ICSI in 2018 were selected randomly. Patients in the two groups were matched for number of gestational sacs, maternal age, infertility type, cause of infertility, fertilization method, endometrial thickness 1 day before embryo transfer and number of embryos transferred. The classification of congenital uterine anomalies was based on the American Fertility Society system (1988). The pregnancy and obstetric outcomes of the didelphic and control groups were compared separately for singleton and twin pregnancies, and for all pregnancies combined. In singleton pregnancies, women with uterus didelphys had increased risk of preterm birth (odds ratio (OR), 4.68; rate difference (RD), 0.14; P < 0.001), Cesarean section (OR, 2.80; RD, 0.17; P = 0.016) and birth weight < 2500 g (OR, 4.06; RD, 0.10; P = 0.017) compared to women with normal uterine morphology. In twin pregnancies, the presence of uterus didelphys was associated with increased risk of preterm delivery (OR, 4.79; RD, 0.37; P = 0.006), perinatal mortality (OR, 3.16; RD, 0.19; P = 0.043) and birth weight < 2500 g (OR, 9.57; RD, 0.35; P = 0.001). The presence of uterus didelphys was associated with significantly increased risk of some adverse pregnancy outcomes compared to pregnancies with normal uterine morphology in women who underwent IVF/ICSI. A twin pregnancy in women with uterus didelphys was associated with worse perinatal outcome. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.