Chorionic villus sampling or CVS is a diagnostic test administered in early pregnancy that can determine whether a fetus possesses certain conditions. Typically, these conditions are chromosomal or genetic, such as Down syndrome or cystic fibrosis. Physicians perform the test by sampling a small bit of tissue from the placenta. Though CVS is an effective way to learn about a baby’s health, there are several risks. In addition, there are two methods for physicians to perform the test: transcervical or transabdominal.


1. Anatomy

The placenta is a temporary organ that connects a developing fetus to its mother’s uterine wall via the umbilical cord. This allows for a number of important functions, including nutrient uptake, gas exchange, waste elimination, and temperature regulation. The chorionic villi are small, wispy projections of tissue that share the fetus’ genetic makeup. In chorionic villus sampling, physicians take a small sample from the chorionic villi and test for any abnormalities. Though most people associate CVS with testing for Down syndrome, the test can detect more than 200 different disorders.

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