What prenatal tests are done in the first trimester?
You can have several tests in your first trimester:
- 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 August 2012