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
Frequently Asked Questions
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.