Vascular anomalies of the umbilical cord: I. Obstetric implications.

Single umbilical artery (SUA) and velamentous insertion of the umbilical cord (VIU) were observed in 0.44 and 2.17%, respectively in a series of 14050 placentae which were systematically examined. The birth weights for both these groups were lower than for the reference material, with the lowest mean value in the SUA-group. The ponderal index, indicating insufficient intrauterine supply of nutrients, was relatively more reduced than the head circumference--especially in the SUA-group. Among twins where only one had VIU most of the VIU-twins showed a comparable lower birth weight than the other twin. The mean gestational age was only moderately reduced in both groups, though there was quite a high number of premature births. Both bilobate placenta and placental infarcts were registered somewhat more frequently in both groups than in the reference material while circumvallate placenta was found more frequently in the SUA-group only. None of the groups showed reduced placental weight when correlated with birth weight.