The missing umbilical artery. I. Prospective study based on a maternity unit

844. The missing umbilical artery. I. Prospective study based on a maternity unit. In a consecutive series of nearly 20,000 freshly delivered placentas, 2 vessels instead of the normal 3 were found in the umbilical cords of 143 (0 72%) infants, 83 females and 60 males. 4 infants were twins: in each instance the co-twin had 3 vessels. The incidence of single umbilical artery (SUA) in multiple pregnancies was slightly less than in singletons. 2 infants with SUA were sibs. There was an increased incidence of major malformations (17-5%), of prematurity (16.5%), and of smallness for dates (34%) among infants with SUA. 25 (17 5%) infants, of whom 19 had a major malformation, died in the perinatal period; of these, 2 had a persistent vitelline artery. (A follow-up study has been carried out on the surviving infants-results to be published.) This investigation into the incidence and significance of SUA is based on what is so far the largest prospective and unselected series collected in a single maternity unit. All placental examinations and necropsies were carried out by one pathologist, all follow-up examinations by one paediatrician