Questions: Which statement about chorionic villus sampling is correct? It enables the physician to study the genetic makeup of the fetus. It is based on a sample of amniotic fluid taken by needle from the mother's abdomen. It is usually conducted by a physician between the 14th and 17th weeks of pregnancy. It reduces the chance of spontaneous abortion.

The answer is the first one: It enables the physician to study the genetic makeup of the fetus.

Explanation for each option:

1. It enables the physician to study the genetic makeup of the fetus.

   • This statement is correct. Chorionic villus sampling (CVS) involves taking a small sample of cells from the placenta, which contains the same genetic material as the fetus. This allows for genetic testing and diagnosis of certain conditions.

2. It is based on a sample of amniotic fluid taken by needle from the mother's abdomen.

   • This statement is incorrect. This describes amniocentesis, not chorionic villus sampling. CVS involves taking a sample of placental tissue, not amniotic fluid.

3. It is usually conducted by a physician between the 14th and 17th weeks of pregnancy.

   • This statement is incorrect. Chorionic villus sampling is typically performed earlier, usually between the 10th and 13th weeks of pregnancy.

4. It reduces the chance of spontaneous abortion.

   • This statement is incorrect. In fact, CVS carries a small risk of causing a miscarriage, so it does not reduce the chance of spontaneous abortion.

Summary: Chorionic villus sampling enables the physician to study the genetic makeup of the fetus by taking a sample of placental tissue. It is not based on amniotic fluid sampling, is performed earlier than the 14th to 17th weeks of pregnancy, and does not reduce the chance of spontaneous abortion.