What is chorionic villi sampling primarily used for?

Chorionic villi sampling (CVS) is primarily used for testing for genetic anomalies in fetal tissue. This prenatal diagnostic procedure allows healthcare providers to obtain a sample of chorionic villi, which are tiny projections from the placenta that share the baby's genetic material. By analyzing this tissue, doctors can identify various genetic disorders, such as Down syndrome, cystic fibrosis, and other chromosomal abnormalities, providing valuable information about the baby’s health early in the pregnancy.

The other options relate to different aspects of prenatal care or assessment. Determining fetal age is typically done through ultrasounds rather than CVS. Withdrawing a sample of amniotic fluid refers to amniocentesis, another prenatal procedure that assesses fetal health but does not use the chorionic villi. Measuring fetal heart rate is accomplished through electronic fetal monitoring and does not involve any genetic testing or tissue sampling. Thus, the primary use of CVS distinctly aligns with genetic testing in fetal tissue.