Prenatal tests

KEY POINTS

  • You get some prenatal tests, like a blood pressure check and a urine test, several times during pregnancy.

  • You get other prenatal tests, like an ultrasound or special blood tests, at certain times during pregnancy or if you have certain problems.

  • Some prenatal tests can help you find out if your baby has certain health conditions, like birth defects and genetic conditions.

  • Talk to your provider about which prenatal tests are right for you.

What are prenatal tests and why are they important?

Prenatal tests are medical tests you get during pregnancy. They help your health care provider find out how you and your baby are doing. 

You get some prenatal tests several times during pregnancy at your prenatal care checkups. You get other tests at certain times during pregnancy or if you have certain problems that may affect your health and your baby’s health. For example, some prenatal tests check for health conditions in your baby, including: 

  • Birth defects. These are health conditions that are present at birth. They change the shape or function of one or more parts of the body. Birth defects can cause problems in overall health, how the body develops or how the body works.
  • Genetic and chromosomal conditions. These conditions are caused by changes in genes and chromosomes. A gene is part of your body's cells that stores instructions for the way your body grows and works. A chromosome is the structure in cells that holds genes. Genetic conditions include cystic fibrosis (also called CF), sickle cell disease and heart defects. A common chromosomal condition is Down syndrome. Sometimes these conditions are passed from parent to child, and sometimes they happen on their own. 

If certain health conditions run in your family, you may want to talk with a genetic counselor. A genetic counselor has training to help you understand about genes, birth defects and other medical conditions that run in families, and how they can affect your health and your baby's health.

What are screening tests and diagnostic tests?

Prenatal tests are either screening tests or diagnostic tests:

  • Screening tests. These tests check if your baby is more likely than others to have a health condition, but they don’t tell you for sure if you baby has a condition. There are no risks to you or your baby when you have a screening test. 
  • Diagnostic tests. These tests tell you for sure if your baby has or doesn’t have a health condition. If a screening test shows your baby is at high risk of a health condition, your provider may recommend a diagnostic test to confirm the results. Some diagnostic tests may have some risks for your baby, like miscarriage. Miscarriage is when a baby dies in the womb before 20 weeks of pregnancy.

Screening test results can help you decide if you want to have a diagnostic test. You may or may not want to know if your baby has a health condition. If you decide to have a diagnostic test, you can learn more about your baby’s condition and how to care for your baby after he’s born. You also can make plans to give birth in a hospital that can give your baby special medical care.

What prenatal tests do you get all through pregnancy?

You can get these prenatal tests several times during pregnancy:

  • Blood pressure check. Your provider checks your blood pressure to make sure you don’t have preeclampsia. Preeclampsia is when a pregnant woman has high blood pressure and signs that some of her organs, like her kidneys and liver, may not be working properly. Preeclampsia can cause serious problems during pregnancy. 
  • Urine test. Your provider checks your urine for infections, like a bladder or kidney infection, and other conditions, like preeclampsia. Having protein in your urine may be a sign of preeclampsia. 
  • Blood tests. Your provider checks your blood for certain infections, like syphilis, hepatitis B and HIV. She also uses a blood test to find out your blood type and Rh factor and to check for anemia. Anemia is when you don't have enough healthy red blood cells to carry oxygen to the rest of your body. Rh factor is a protein that most people have on their red blood cells. If you don’t have it and your baby does, it can cause Rh disease in your baby. Treatment during pregnancy can prevent Rh disease.  

Your provider also checks your weight at each prenatal care checkup to make sure you’re gaining the right amount.

What prenatal tests are done in the first trimester? 

You can have several tests in your first trimester (months 1, 2 and 3). Talk to your provider to find out which tests are right for you. 

  • Carrier screening for genetic conditions. This screening test checks your blood or saliva to see if you’re a carrier of certain genetic conditions that could affect your baby. If you’re a carrier, you don’t have the condition yourself, but you have a gene change (a change in a gene) for it that you can pass to your baby. If both you and your partner are carriers of the same condition, the risk that your baby has the condition increases. Carrier screening can be done before pregnancy or during the early weeks of pregnancy. If results show that you or your partner is a carrier, you may be able to find out if your baby has the condition or is a carrier of the condition. All women can have carrier screening for CF, spinal muscular atrophy (also called SMA), thalassemias and hemoglobinopathies. CF is a condition that affects breathing and digestion. SMA attacks nerve cells in the spinal cord. It weakens muscles and can affect movement, breathing and swallowing. Thalassemias and hemoglobinopathies are blood conditions that affect red blood cells. Some women get carrier screening for conditions, like Fragile X syndrome and Tay Sachs disease. These conditions run in families or ethnic groups. An ethnic group is a group of people, often from the same country, who share language or culture.
  • Cell-free fetal DNA testing (also called noninvasive prenatal screening or testing). This screening test checks your blood for your baby’s DNA to see if he may have certain genetic conditions, like Down syndrome. This test is done after 9 weeks of pregnancy. Your provider may recommend the test if an ultrasound shows that your baby may have a birth defect or if you've already had a baby with a birth defect. It’s not recommended if you’re not at risk for having a baby with a birth defect or if you’re pregnant with multiples (more than one baby, like twins or triplets). The test is called noninvasive because it’s a simple blood test that doesn’t require any other tools that break the skin or enter your body. If you have this test, your provider may recommend you have a diagnostic test, like amniocentesis, to confirm the results.
  • Chorionic villus sampling (also called CVS). This diagnostic test checks tissue from the placenta to see if your baby has a genetic condition, like Down syndrome. CVS is done at 10 to 13 weeks of pregnancy. Your provider may want you to have CVS if you’re older than 35, if genetic conditions run in your family, or if your first-trimester screening shows that your baby is at increased risk for birth defects.
  • Early ultrasound (also called first-trimester ultrasound). Ultrasound uses sound waves and a computer screen to make a picture of your baby inside the womb. Your provider may use early ultrasound to make sure that you’re pregnant or to date your pregnancy so you know how far along in pregnancy (how many weeks) you are.
  • First-trimester screening. This screening test includes a blood test and an ultrasound to see if your baby may be at risk for some birth defects, like Down syndrome and heart defects. The test usually is done at 11 to 14 weeks of pregnancy.

What tests are done in the second trimester? 

Your provider may offer you these prenatal tests in your second trimester (months 4, 5 and 6 of pregnancy):

  • Maternal blood screening (also called quad screen). This screening test checks your blood to see if your baby may be at risk for some birth defects, like Down syndrome. It’s called a quad screen because it measures four substances in your blood: alpha-fetoprotein (AFP), estriol, human chorionic gonadostropin (hCG) and inhibin A. The test is done at 15 to 22 weeks of pregnancy. 
  • Amniocentesis (also called amnio). Amnio is a diagnostic test of the amniotic fluid from around your baby to see if he has a birth defect or genetic condition, like Down syndrome. The test usually is done at 15 to 20 weeks of pregnancy. Your provider may want you to have an amnio for the same reasons as for CVS. You also may have amnio later in pregnancy to check your baby’s lungs or to see if he has certain infections.
  • Ultrasound. Your provider uses ultrasound to check your baby’s growth and for birth defects. It’s usually done at 16 to 20 weeks of pregnancy. 
  • Glucose screening. This screening test checks to see if you may have gestational diabetes. This is a kind of diabetes that some women get during pregnancy. You get this test at 24 to 28 weeks of pregnancy.

What tests are done during the third trimester? 

In your last trimester (months 7, 8 and 9 of pregnancy), your provider does a test for group B strep (also called GBS). Group B strep is an infection you can pass to your baby during birth. The test checks fluid from your cervix to see if you have GBS. You get this test at 35 to 37 weeks of pregnancy.

What are kick counts and how do you do them?

Kick counts (also called fetal movement counts) is a way for you to track how often your baby moves. By about 5 months (20 weeks) of pregnancy, you should start to feel your baby move in your belly. Your baby can turn from side to side and sometimes head over heels. Tell your provider if:

  • You’re at about 20 weeks of pregnancy and haven’t felt your baby move.
  • You’re worried that your baby isn’t moving.
  • You notice a change in how often your baby moves, especially if he moves less often. 

Your provider may ask you to do kick counts to see when and how often your baby moves. Here are two ways to do kick counts:

  1. Every day, time how long it takes for your baby to move ten times. If it takes longer than 2 hours, tell your provider.
  2. See how many movements you feel in 1 hour. Do this three times each week. If the number changes, tell your provider.  

You can do kick counts even into your third trimester. If your provider’s concerned about your baby’s movements, she may do other tests to check on your baby’s health.  

More information

Last reviewed: May, 2017