Guide to Prenatal Testing

When you’re pregnant, prenatal tests give you information about your health and your baby’s. They help detect any problems that could affect them, like birth defects or genetic diseases. The results can help you make the best health care decisions before and after your child is born.

Prenatal tests are helpful, but it’s important to know how to interpret what they find. A positive test result doesn’t always mean your baby will be born with a disorder. You’ll want to talk with your doctor, midwife, or other health care provider about what the tests mean and what you should do once you have the results.

Doctors recommend some prenatal tests for all pregnant women. Only some women will need other screening tests to check for certain genetic problems.

Routine Prenatal Tests

There are different prenatal tests you can get in your first, second, and third trimester. Some check your health, and others get information about your baby.

Throughout your pregnancy, you’ll get routine exams to make sure you’re healthy. Your health care provider will check samples of your blood and urine for certain conditions, including:

• HIV and other sexually transmitted diseases
• Anemia
• Diabetes
• Hepatitis B
• Preeclampsia, a type of high blood pressure

They’ll also check your blood type and whether your blood cells have a protein called the Rh factor. You may also get:

• Pap smear
• Group B Strep screening. Your doctor will swab the skin in and around your vagina to check for this type of bacteria. This usually happens in the last month before you give birth.
• Ultrasound. This technology uses sound waves to make pictures of your baby and your organs. If your pregnancy is normal, you’ll have it twice, once near the beginning to see how far along you are, and the second time around 18-20 weeks to check your baby’s growth and make sure their organs are developing properly.

Prenatal Genetic Tests

Doctors also can use prenatal tests to look for signs that your baby is at risk for certain genetic disorders or birth defects. You don’t have to have these tests, but your doctor may suggest some to make sure your baby is healthy.

Other Tests

If you get a positive result on a screening, your doctor can use other tests to look for a problem.

Amniocentesis. Using a thin needle in your belly, your doctor will take a sample of the fluid that surrounds your baby and check it for genetic disorders or birth defects. The procedure does carry some risk. About 1 in 300 to 500 women will miscarry because of amniocentesis. Your doctor can tell you if it’s important for you to have this.

Chorionic villus sampling (CVS). Doctors take a small piece of your placenta by putting a needle through your belly or a small tube up your vagina. They test the sample for Down syndrome and other genetic conditions. Only some high- risk women will need this test, usually if a screening found a risk of a birth defect. The procedure will tell you for sure if there’s a problem, but it also comes with a risk of miscarriage that’s similar to amniocentesis. Talk to your doctor about whether you should have CVS.

What Do I Do Once I Have the Results?

Prenatal test results can help you make important health care decisions. But it’s important to remember that many of them tell you it’s possible, but not certain, that your baby will be born with a disorder. No test is 100% accurate.

Talk to your doctor about the results you get and what they mean. A genetics counselor can also help you decide what to do after a positive result and what life will be like for your child if they have a disorder.

Questions for Your Doctor

If your doctor recommends prenatal testing, consider asking:

• Why do I need these tests?
• What will the results tell me? What will they not show?
• What happens if I don't get the test?
• What will I do with the results?
• How accurate are the tests?
• What are the risks?
• How long will it take to get the results?
• What does it feel like?
• How much do they cost?
• Will my insurance cover them?
• Will anyone else (like my insurance company) have access to the results, especially of genetic tests?
• What will the results mean for my family?
• Can I decide not to get the results even if the test has already been done?
• Where do I get the tests done?

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