- To investigate the influence of gestational diabetes mellitus (GDM) on maternal and neonatal outcomes in twin pregnancies. A retrospective population-based study was conducted, comparing maternal and neonatal outcome in women carrying twins with and without GDM. Deliveries occurred in a tertiary medical center between the years 1988 and 2010. Multivariable analysis was used to control for confounders. The study population included 4,428 twin pregnancies, of these 341 (7.7 %) were complicated with GDM. Twin pregnancies complicated with GDM had higher rates of fertility treatment, chronic hypertension, preeclampsia and cesarean deliveries (CD). Nevertheless, using a multivariable analysis, with CD as the outcome variable, controlling for confounders such as maternal age, fertility treatments and hypertensive disorders, GDM in twins was not found to be an independent risk factor for CD (adjusted OR = 1.8, 95 % CI 0.9-1.4; P = 0.18). Rates of low 5 min Apgar scores (<7) and perinatal mortality were lower among twins with GDM (2.9 % vs. 5.3 %, OR = 0.5, 95 % CI 0.3-0.8 0; P = 0.005 and 2.3 % vs. 4.4 %, OR = 0.5, 95 % CI 0.3-0.8; P = 0.005, respectively). In our population, GDM in twin pregnancies was not associated with increased rates of adverse perinatal outcomes. In addition, GDM was not found to be an independent risk factor for CD in twin pregnancies.