Prenatal tests

Prenatal tests are medical tests you get during pregnancy. They help your health care provider find out how you and your baby are doing. Some of these tests, like blood pressure checks and urine tests, are routine. You get these at almost every checkup. You get other tests at certain times during pregnancy or only if you have certain problems. Talk to your provider about which test you should have.

What prenatal tests are done in the first trimester? 

You can have several tests in your first trimester. Talk to your provider to find out which tests are right for you. 

  • Cell-free fetal DNA testing (also called noninvasive prenatal testing). Tests your  blood for your baby’s DNA to see if he has certain genetic conditions, like Down syndrome. You can have this test after 10 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 for women who aren't likely to have a baby with a birth defect or who are pregnant with multiples (more than one baby, like twins or triplets).
  • Chorionic villus sampling (CVS). Tests the tissue around the baby to see if he has a genetic condition, like Down syndrome. The test usually is done between 10 and 12 weeks of pregnancy. Your provider may want you to have CVS if you’re older than 35, if genetic problems run in your family, or if your first-trimester screening shows that your baby is at increased risk for birth defects.
  • Cystic fibrosis (CF) carrier screening. Tests to see if you have the gene that causes CF. CF is a disease that affects breathing and digestion. If you and your partner have the gene, you can pass CF to your baby. You and your partner can have this test any time during pregnancy.
  • Early ultrasound. Confirms (makes sure) that you’re pregnant. It also dates the pregnancy, so you know your baby’s age.
  • First-trimester screening. Tests your blood to see if your baby is at risk for some birth defects, like Down syndrome and heart defects. You get an ultrasound as part of this test. The test usually is done at 11 to 13 weeks of pregnancy.

What tests are done during the second trimester? 

As you get further along in your pregnancy, your provider may offer you these prenatal tests:

  • Maternal blood screening. Tests your blood to see if your baby is at risk for some birth defects, like Down syndrome and heart defects. The test measures four substances in the mother's blood: alpha-fetoprotein (AFP), estriol, human chorionic gonadostropin (hCG) and inhibin A. The test is done at 15 to 20 weeks of pregnancy.
  • Amniocentesis. Also called amnio. Tests the amniotic fluid from around your baby to see if he has a genetic condition, like Down syndrome. The test usually is done at 15 to20 weeks of pregnancy. Your provider may want you to have an amnio for the same reasons as for CVS.
  • Ultrasound. Helps your provider make sure your baby is growing and check for birth defects. It’s usually done at 18 to 20 weeks of pregnancy.
  • Glucose screening. Tests to see if you have gestational diabetes. This is a kind of diabetes that some women get during pregnancy. The test is done 24 to 28 weeks of pregnancy.

What test is done during the third trimester? 

In your last trimester, 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. The test is done at 35 to 37 weeks of pregnancy.

Last reviewed July 2013

See also: Vaccinations and pregnancy, Choosing your prenatal care provider

 

Most common questions

What is transabdominal ultrasound?

When you hear about ultrasound during pregnancy, it’s most likely a transabdominal ultrasound. This is a prenatal test that uses sound waves to show a picture of your baby in the uterus (womb). Your health care provider uses it to check your baby’s health. Most women get an ultrasound at 18 to 20 weeks of pregnancy.

During an ultrasound, your provider moves a plastic tool, called a transducer, across your belly. The transducer sends sound waves into your uterus. The waves bounce around to create a picture of your baby on a monitor. To get a better picture, your provider covers your belly with a thin layer of gel. This helps the sound waves move more easily.

Your provider measures your baby’s body throughout the test. Depending on your baby’s position, your provider may point out his hands, legs and other body parts. You should be able to tell if your baby’s a boy or a girl, so be sure to tell your provider if you don’t want to know!

You may need to have a full bladder during the test. This prevents pockets of air in your bladder from affecting the picture. Ultrasound is painless, but having a full bladder may be uncomfortable.

What is first trimester ultrasound?

First-trimester ultrasound (also called early ultrasound) is a prenatal test that uses sound waves to show a picture of your baby in the uterus (womb). Some providers may use this kind of ultrasound to make sure your baby’s organs are growing and developing normally.

Your health care provider uses it to check your baby’s health. A first-trimester ultrasound takes place before 14 weeks of pregnancy.

The kind of first-trimester ultrasound you have depends on the type of information your provider needs. Your provider usually does ultrasound by moving a plastic tool, called a transducer, across your belly. This is called transabdominal ultrasound. You also can have a transvaginal ultrasound, which means it’s done in the vagina (birth canal). Both kinds usually take about 15 to 20 minutes.

Your provider can use first-trimester ultrasound to:

See also: Ultrasound

What is 4-D ultrasound?

4-D ultrasound is a prenatal test that uses sound waves to show a three-dimensional picture of your baby in the uterus (womb) and shows your baby’s movement. 3-D images are almost as clear as a photograph, and 4-D is a moving-picture version or video. Some providers may use this kind of ultrasound to make sure your baby’s organs are growing and developing normally.

You may know of some places, like stores in a mall, that aren’t run by doctors or other medical professionals that offer “keepsake” 3-D or 4-D ultrasound pictures or videos for parents. The American College of Obstetricians and Gynecologists, the Food and Drug Administration and the American Institute of Ultrasound in Medicine do not recommend these non-medical ultrasounds. The people doing them may not have medical training and may give you wrong or even harmful information.

What is 3-D ultrasound?

3-D ultrasound is a prenatal test that uses sound waves to show a three-dimensional picture of your baby in the uterus (womb). Some providers may use this kind of ultrasound to make sure your baby’s organs are growing and developing normally.

The 3-D ultrasound is almost as clear as a photograph. A moving-picture version is called 4-D ultrasound.

You may know of some places, like stores in a mall, that aren’t run by doctors or other medical professionals that offer “keepsake” 3-D or 4-D ultrasound pictures or videos for parents. The American College of Obstetricians and Gynecologists, the Food and Drug Administration and the American Institute of Ultrasound in Medicine do not recommend these non-medical ultrasounds. The people doing them may not have medical training and may give you wrong or even harmful information.

See also: Ultrasound

What is Doppler ultrasound

Doppler ultrasound is a kind of prenatal test that can be used to check a baby’s health in high-risk pregnancies. Providers usually use Doppler ultrasound during the last trimester, but it may be done earlier.

During Doppler ultrasound, your provider uses a plastic tool called a transducer to measure the blood flow in the umbilical cord and some of your baby’s blood vessels. This test shows if your baby is getting enough oxygen. Your provider also can listen to your baby’s heartbeat using Doppler ultrasound.

Some providers use Doppler ultrasound to check mothers with Rh disease. This is a condition where a difference between the mother’s blood and baby’s blood can cause a dangerous kind of anemia in the baby. Anemia is when the body doesn’t have enough red blood cells or the red blood cells are too small. When the condition is found early and treated, most affected babies survive.

What is transvaginal ultrasound?

Transvaginal ultrasound is a prenatal test that uses sound waves to show a picture of your baby in the uterus (womb). Your health care provider uses transvaginal ultrasound to check your baby’s health. It’s often used for early ultrasound in the first trimester.

During the test, your provider moves a thin, wand-like transducer into the vagina. You lay on your back with your feet in stirrups during the exam. You may feel some pressure from the transducer, but it shouldn’t cause pain.

Transvaginal ultrasound can be used throughout pregnancy to check for problems with the cervix (opening to the uterus) and lower uterus.

See also: Ultrasound

How is blood pressure measured?

Blood pressure is the force of blood that pushes against the walls of your arteries. Arteries are blood vessels that carry blood away from your heart to other parts of the body. If the pressure in your arteries becomes too high, you have high blood pressure. High blood pressure is also called hypertension.

At each prenantal care visit, your health care provider checks your blood pressure. To do this, she wraps an inflatable cuff around your upper arm. She pumps air into the cuff to measure the pressure in your arteries when the heart contracts (gets tight) and then relaxes.

Your blood pressure reading is given as two numbers: the top (first) number is the pressure when your heart contracts and the bottom (second) number is the pressure when your heart relaxes. A healthy blood pressure is 110/80. High blood pressure happens when the top number is 140 or greater, or when the bottom number is 90 or greater

Your blood pressure can go up or down during the day. Your provider can re-check a high reading to find out if you have high blood pressure during pregnancy.

Last reviewed March 2012

See also: High blood pressure during pregnancy, Preeclampsia, HELLP syndrome

Can a rubella shot hurt my baby during pregnancy?

If you got your rubella shot around the time you got pregnant, it's unlikely that your baby will be harmed by the vaccine. However, it's best to wait to get pregnant for 28 days after vaccination because there is a very small risk of potentially hurting the baby. To date, there hasn't been any birth defects reported that are attributed to the rubella vaccine. In any case, the risk of harming your baby by getting the vaccine at the time you got pregnant is much lower than the risk of harming your baby if you caught rubella during pregnancy.

I couldn't see my baby at my 7 week ultrasound. Why?

At the 7th week of pregnancy, your baby is about ½ an inch long or the size of a blueberry. He's very small. When a transabdominal ultrasound (done on your belly) is done at such an early stage, it's possible that the baby can't be seen. It could be because it's too early in the pregnancy or because you conceived a little later than what you thought. Your health care provider might recommend a transvaginal ultrasound (done inside the vagina) to help see the baby more clearly.

What are choroid plexus cysts?

The choroid plexus is the area of the brain that produces the fluid that surrounds the brain and spinal cord. This is not an area of the brain that involves learning or thinking. Occasionally, one or more cysts can form in the choroid plexus. These cysts are made of blood vessels and tissue. They do not cause intellectual disabilities or learning problems. Using ultrasound, a health care provider can see these cysts in about 1 in 120 pregnancies at 15 to 20 weeks gestation. Most disappear during pregnancy or within several months after birth and are no risk to the baby. They aren't a problem by themselves. But if screening tests show other signs of risk, they may indicate a possible genetic defect. In this case, testing with higher-level ultrasound and/or amniocentesis may be recommended to confirm or rule out serious problems.

©2013 March of Dimes Foundation. The March of Dimes is a non-profit organization recognized as tax-exempt under Internal Revenue Code section 501(c)(3).