The findings of a single umbilical aery on examination of the umbilical cord after delivery is

The absence of one umbilical aery occurs in 0.7 to 0.8% of all umbilical cords of singletons, in 2.5% of all abouses, and in approximately 5% of at least one twin. The incidence of a single aery is significantly increased in newborns of diabetic mothers, and it occurs in white infants twice as often as in newborns of black women. The incidence of major fetal malformations when only one aery is identified has been repoed to be as high as 18%, and there is an increased incidence of overall fetal moality. The finding is an indication to offer amniocentesis, cordocentesis, or chorionic villus sampling to study fetal chromosomes, although there is debate about whether this should be done when there is only a truly isolated finding of single umbilical aery.