The umbilical artery on one side is slightly thin, and a low risk result after non-invasive DNA testing indicates that the fetus is generally not at risk. Non-invasive DNA testing is done to screen the fetus for chromosomal disorders such as Down syndrome, trisomy 13, trisomy 18, etc. If the test results indicate a low risk, the fetus is generally not at risk, even if the umbilical artery is single. If the non-invasive DNA test suggests a low risk, then the fetus is generally not at risk for chromosomal abnormalities, even if there is a single umbilical artery. If the umbilical artery is only slightly thin on one side, the risk of fetal malformations is even lower. Pregnant women are advised not to be over-anxious once they realize that one side of the umbilical artery is slightly thin and is found to be at low risk after the non-invasive DNA test, but to relax, take good care of themselves during pregnancy, and consult a doctor in case of any abnormality.