Alpha-fetoprotein Screening (AFP)–A simple blood test that poses no risk to the fetus, AFP screening measures the levels of alpha-fetoprotein in the mother’s blood. Abnormal levels can indicate a brain or spinal cord defect, the presence of twins, a miscalculated due date, or an increased risk of Down syndrome. Because AFP levels can be elevated for a number of reasons, a positive test is usually repeated or followed up by other tests before a diagnosis is made. Very few women with elevated AFP levels are found later to have babies with birth defects.
Blood type, Rh factor, and antibody screening
At your first prenatal visit, your practitioner will check your blood to see whether it’s type O, A, B, or AB, and whether it’s Rh-negative.
If you’re Rh-negative, you’ll get a shot of Rh immune globulin at least once during your pregnancy, and another after you give birth if your baby turns out to be Rh-positive.
This shot will protect you from developing antibodies that could be dangerous during this pregnancy or in future pregnancies. (Note: If the baby’s father is also Rh-negative, your baby will be too, so you won’t need the shot.)
Your blood will also be checked for Rh antibodies as well as some other antibodies that may affect your pregnancy.
Complete blood count
A complete blood count will tell your practitioner if you have too little hemoglobin in your red blood cells (a sign of anemia) and, if so, whether it’s likely to be the result of iron deficiency.
If you’re iron deficient, your practitioner will recommend that you take iron supplements and eatmore iron-rich foods, such as lean meat.
The test also counts your platelets and white blood cells. (An elevated number of white blood cells could indicate an infection.)
Rubella (German measles) immunity
This test, called a rubella titer, checks the level of antibodies to the rubella virus in your blood to see whether you’re immune. Most women are immune to rubella, either because they’ve been vaccinated or had the disease as a child.
During pregnancy, the rubella virus can cause a miscarriage, preterm birth, or stillbirth, as well as a variety of serious birth defects, depending on how far along you are when you contract the virus. So if you aren’t immune, it’s very important to avoid anyone who has the infection and forgo travel to foreign countries where the disease is still prevalent. (Fortunately, rubella is rare in the United States.)
Although you can’t be vaccinated while you’re pregnant, you should get the vaccine after you give birth to protect future pregnancies.
Hepatitis B testing
Many women with this liver disease have no symptoms and can unknowingly pass it to their baby during labour or after birth. This test will reveal whether you’re a hepatitis B carrier.
If you are, your practitioner will protect your baby by giving him an injection of hepatitis B immune globulin as well as his first shot of the hep B vaccine within 12 hours of birth. (He’ll get the second shot at 1 or 2 months and the third at 6 months.) All members of your household should be tested and vaccinated if you’re a carrier.
This sexually transmitted infection (STI) is relatively rare today, but all women should be tested because if you have syphilis and don’t treat it, both you and your baby could develop serious problems. In the unlikely event that you test positive, you’ll be given antibiotics to treat the infection.
The Centers for Disease Control and Prevention, the American Congress of Obstetricians and Gynecologists, and a host of other organizations recommend that all pregnant women be tested for the human immunodeficiency virus (HIV), the virus that causes AIDS. If you test positive for HIV, you and your baby can get treatment that will help maintain your own health and greatly reduce the chance that your baby will become infected with the virus.
Other blood tests
If you’re not sure whether you’ve ever had chicken pox or been vaccinated against it, you can be tested to see if you’re immune. If you’re at high risk for diabetes, a glucose challenge test may be done at your first visit.
In addition, all women should be offered first-trimester screening for Down syndrome and some other chromosomal abnormalities. This generally involves a blood test as well as an ultrasound to measure the baby’s nuchal fold.
Your caregiver may recommend some other blood tests for genetic disorders, depending on your situation and preferences. Some of these, like the test that determines whether you’re a cystic fibrosis carrier, may be offered to you even if you’re not in a high-risk category.
Unless there’s a problem that needs to be addressed right away or you’re particularly concerned about a certain test, your practitioner will generally wait until your next appointment to review your test results with you.