Single artery may b normal but to b evaluate to find any. Defect if anomaly scan normal than evaluate again up to 20to 30 week Maternal serum afp hcg to b done if suspected

It is not a major issue. Correlate with fetal Doppler

It is common Only little more precautions what you require Many cases end up in premature delivery,,,

Hi there, Umbilical cord had two arteries which help in providing oxygen and nutrition  to the baby. Single umbilical artery  is a sign of some associated congenital anomaly. Your baby needs further evaluation for that. And in certain percentage of people isolated single umbilical artery may not cause any problem in the baby. But your baby needs continuous monitoring till delivery as single artery may not provide adequate nutrition to the baby. And baby's growth may get affected.