Purpose of Investigation: To evaluate the maternal and neonatal outcomes in twin pregnancies according to chorionicity (monochorionic (MC) versus dichorionic (DC) and type of conception [spontaneously conceived (SC) versus assisted reproduction technology (ART)]. Materials and Methods: A retrospective study of 196 twin pregnancies admitted to the Department of Gynecology, Obstetrics and Urology of the University of Rome Sapienza, from January 2008 to April 2013. Results: There were 55 MC and 141 DC twin pregnancies (82 SC and 59 ART). MC twin pregnancies had a higher incidence of preterm birth (p < 0.008), twin-twin transfusion syndrome (TTTS) (p < 0.021), and intrauterine growth restriction (IUGR) (p < 0.05). MC pregnancies had lower neonatal birth weight (p < 0.05), and lower Apgar score. ART DC pregnancies had a higher incidence of preterm delivery (p < 0.05). Conclusions: MC twin pregnancy is associated with higher risk of adverse maternal and perinatal outcomes. In the DC subgroup, ART is associated to a higher incidence of preterm delivery.