Types of prenatal testing

The two main types of prenatal testing are:

• Screening tests. Prenatal screening tests can identify whether your baby is more or less likely to have certain birth defects, many of which are genetic disorders. These tests include blood tests, a specific type of ultrasound and prenatal cell-free DNA screening. Prenatal screening tests are usually offered during the first or second trimester. Screening tests can't make a definitive diagnosis. If results indicate an increased risk for a genetic disorder, your health care provider will discuss your options for a diagnostic test to confirm the diagnosis.
• Diagnostic tests. If a screening test indicates a possible problem — or your age, family history or medical history puts you at increased risk of having a baby with a genetic problem — you might consider an invasive prenatal diagnostic test. A diagnostic test is the only way to be sure of a diagnosis. Some diagnostic tests, such as chorionic villus sampling and amniocentesis, carry a slight risk of miscarriage.