Which method tests a fetus for genetic abnormalities?

Amniocentesis is the method used to test a fetus for genetic abnormalities. This procedure involves extracting a small amount of amniotic fluid that surrounds the fetus, which contains fetal cells. These cells can then be analyzed for chromosomal abnormalities, such as Down syndrome or other genetic disorders. The timing of this procedure typically occurs between the 15th and 20th weeks of pregnancy, offering critical information about the fetus's genetic health.

In contrast, artificial selection and hybrid vigor relate more to breeding practices and population genetics than to fetal testing. Artificial selection involves manipulating breeding to enhance desirable traits in organisms. Hybrid vigor refers to the improved biological quality that can occur in hybrid offspring due to genetic diversity. In vitro fertilization is a reproductive technology wherein an egg and sperm are combined outside the body, which may lead to embryo testing for some genetic conditions but is not directly intended for testing existing fetuses for abnormalities like amniocentesis.