Issues with single umbilical artery?

Majority no problem: Usually the cord has 2 arteries and a vein. It is found in about 5% of pregnancies. The vast majority have no problems at birth, however in about a fourth of these kids there is a higher incidence of malformations that could be in the GI tract, the heart or the nervous system. Also it is associated with higher incidence of chromosomal anomalies like trisomy 18 or trisomy 13.

Sometimes: If there are no other anomoies, no. However, if there is concern for mid-line defects, a renal ultrasound is necessary to make sure kidneys are ok.