A normal fetal umbilical cord contains two umbilical arteries and one umbilical vein encased in Wharton’s jelly. A single umbilical artery is a common umbilical cord abnormality that can pose risks to the fetus's health if not detected early.

NIPT is a non-evasive screening test that is increasingly used and has a very high value for prenatal screening. However, when undergoing and interpreting the test results, pregnant women need to understand certain information about the test's value. It is especially important to understand that any test has a certain rate of false-positive and false-negative results. For NIPT, the positive predictive value for common trisomies is around 90%. This can be simply understood as approximately 10% of women with abnormal test results actually have a normal fetus. So, what are the causes of false-positive and false-negative results in NIPT?