['To clarify actual differences in the neonatal as well as maternal outcome between completed twin vaginal delivery and cesarean delivery.', "We collected the data from women with a twin pregnancy who delivered two live fetuses between 1 January and 31 December 2014 at 20 teaching\u2009hospitals (1) (1) PARTICIPANTS: Adachi Hospital, Hyogo Prefectural Amagasaki General Medical Center, Japan Baptist Hospital, Kitano Hospital, Kobe City Medical Center General Hospital, Kosaka Women's Hospital, Kurashiki Central Hospital, Kyoto University Hospital, Mitsubishi Kyoto Hospital, Nagahama Red Cross Hospital, National Hospital Organization Kyoto Medical Center, National Hospital Organization Osaka National Hospital, Osaka Red Cross Hospital, Otsu Municipal Hospital, Otsu Red Cross Hospital, Red Cross Wakayama Medical Center, Saiseikai Noe Hospital, Shizuoka General Hospital, Takamatsu Red Cross Hospital and Tenri Hospital. in Japan. Only the cases that were retrospectively regarded as eligible for planned vaginal delivery were analyzed according to the actual mode of delivery.", "Umbilical arterial blood pH (UmA-pH) of the second twin was slightly but significantly lower in the vaginal delivery group (7.26\u2009±\u20090.009) than in a cesarean delivery group (7.30\u2009±\u20090.006). Vaginal delivery was the only independent risk factor for second twin's UmA-pH \u2009<7.20. Intrapartum blood loss was significantly larger in the cesarean delivery group (1444\u2009±\u200963\u2009g) than in the vaginal delivery group (820\u2009±\u2009109\u2009g). Cesarean delivery was an independent risk factor for intrapartum blood loss\u2009≥1500\u2009g."] Is twin vaginal delivery associated with lower umbilical arterial blood pH of the second twin and less intrapartum blood loss?