Prenatal tests can detect some potential problems early so that steps can be taken to ensure the best possible outcome for you and your baby.

Some screening tests are performed on almost all pregnant women. Other screening tests are performed only if the parents have specific risk factors for certain conditions.

Diagnostic tests can also be done to determine if your baby is at risk of developing certain conditions or to provide additional information about your baby.

Your health care professional can best advise which prenatal tests are most appropriate for you. Our guide provides an overview of common prenatal tests.

The following tests are based on U.S. procedures. You can consult your health care professional for a list of procedures in your country.

Who is tested: Almost all pregnant women

When: Usually at first prenatal visit

How: Blood drawn from your arm is examined in a laboratory

What this test checks:

Blood type and presence of Rh antibody Why: If your fetus’s blood has the Rh antibody (usually called “Rh positive") and your body lacks the Rh antigen (usually called “Rh negative"), problems may arise. Your body may react as if it were allergic to the fetus. However, if health care professionals are aware of this situation, you will receive special care during pregnancy to help prevent complications.

Hematocrit and hemoglobin levels Why: These levels help check for anemia, a common complication of pregnancy that often results from iron deficiency. Anemia can make you less able to tolerate hemorrhage during delivery, and can increase the risk of infection. It may also increase the risk of low birthweight and preterm delivery. If iron deficiency anemia exists, it can be treated with therapeutic doses of iron.

Presence of syphilis Why: If you have this sexually transmitted disease, you should be treated to avoid transmitting it to your baby.

Presence of rubella immunity Why: If your test shows that you are not immune to rubella, also called German measles, you should avoid contact with anyone who has the disease while you are pregnant and get vaccinated after your baby is born. Rubella can cause birth defects if contracted during pregnancy.

Presence of chickenpox immunity Why: If your test shows that you are not immune to chickenpox, you should avoid contact with anyone who has the disease while you are pregnant. Chickenpox can cause birth defects if contracted during pregnancy.

Presence of hepatitis B virus Why: If you have this infection, you and your baby should be treated.

Presence of human immunodeficiency virus (HIV) Why: HIV is the virus that causes acquired immunodeficiency syndrome (AIDS). If you have this infection, you can be given medication to reduce the risk of transmitting it to your baby.

Risks: None