Every woman has certain tests during pregnancy. Some women, depending on their age, family history, or ethnicity, may undergo additional testing.
Some tests are screening tests, and others are diagnostic tests. If your health care provider orders a screening test, keep in mind that such tests do not diagnose problems. They evaluate risk. So a screening test result that comes back abnormal does not mean there is a problem with your infant. It means that more information is needed. Your health care provider can explain what the test results mean and possible next steps.
The types of tests you may have during pregnancy include:
Routine Tests
Glucose challenge screening. Usually given between 24 and 28 weeks of pregnancy, this screening assesses your risk for gestational diabetes. You will consume a sugary drink and get a blood test 1 hour later to measure your blood sugar levels. If you are at high risk—for example, if you have a family history of diabetes, are obese, had a large baby in a previous pregnancy, or are having twins—you should discuss this with your health care provider get a test for blood glucose earlier in your pregnancy.
Group B streptococcus (pronounced STREP-tuh-KOK-uhss) infection screening. This test is performed between 35 and 37 weeks of pregnancy to look for bacteria (GBS) that can cause pneumonia or other serious infections in your infant. Swabs will be used to take cells from your vagina and rectum. Women who test positive for GBS will need antibiotics when in labor.
Ultrasound exam. You will likely have an ultrasound exam between 18 and 20 weeks of pregnancy to check for any problems with the developing fetus. During an ultrasound exam, gel is spread on your belly and a special tool is moved over it to create a "picture" of the fetus on a monitor.
Urine test. At each prenatal visit, you will give a urine sample, which will be tested for signs of diabetes, urinary tract infections, and preeclampsia.
Screening for Chromosomal and Neural Tube Defects (NTDs) and Other Conditions
Nuchal translucency (pronounced NOO-kuhl trans-LOO-sen-see) screening. This screening test uses ultrasonography to measure the thickness of the back of the fetus's neck between 11 and 14 weeks. This information, combined with the mother's age and the results of the serum screen, helps health care providers determine the fetus's potential risk for chromosomal abnormalities and other problems.
First trimester screen. Blood is drawn to test for PAPP-A and free beta-hCG (or hCG) and may be combined with performing a nuchal translucency ultrasound. This test will provide the risk for Down syndrome as well as other chromosomal problems.
Maternal serum screen (also called quad screen, triple test, triple screen, multiple marker screen, or AFP). Blood is drawn to measure the levels of certain substances that determine the risk of the fetus having chromosomal abnormalities and NTDs. This screening test is done between 15 and 20 weeks of pregnancy.
Chorionic villus (pronounced KOR-ee-ON-ihk VIL-uhss) sampling (CVS). If your fetus is at risk for a chromosomal defect or other genetic disorders, your doctor may recommend this test when you are between 10 and 13 weeks pregnant. In this test, a needle is inserted through the cervix or the abdomen to remove a small sample of cells from the placenta.
Amniocentesis (pronounced AM-nee-oh-sen-TEE-sis). Given between 15 and 20 weeks of pregnancy, this test is used to diagnose chromosomal disorders, such as Down syndrome and your infant's risk for NTDs, such as spina bifida. After a local anesthetic is given, a thin needle is inserted into the abdomen to draw out a small amount of amniotic fluid and cells from the sac surrounding the fetus. The fluid is sent to a lab for testing.
Cell-free fetal DNA. A new, noninvasive test uses the mother's blood to look for increased amounts of material from chromosomes 21, 18, and 13. This test can be given as early as 10 weeks to women whose age, family history, or standard screening results put them at higher risk for having a child with a chromosome disorder. The test is not recommended for women who are at low risk or are carrying multiple fetuses.
Carrier screening for cystic fibrosis (CF). A blood or saliva test determines if you and your partner are carriers for this genetic disease that affects breathing and digestion. Both parents must be a carrier for their child to get CF.
Additional Testing that Your Health Care Provider May Recommend
Glucose tolerance test. If the 1-hour glucose challenge screening is above a certain level, your health care provider may order this test. You will fast for at least 8 hours before the test. Your blood is drawn to test your "fasting blood glucose level." You will consume a sugary drink, and your blood will be taken every hour for 3 hours to see how your body reacts to the sugar. You may then be diagnosed with gestational diabetes.
Non-stress test. This test is performed in the third trimester (28 weeks or later) to monitor the fetus's health. A belt placed around your belly measures the fetal heart rate while the fetus is at rest and while the fetus is moving or kicking. This test can determine if the fetus is getting enough oxygen.
Biophysical profile (BPP). This test, given in the third trimester of pregnancy, monitors the fetus's breathing, movement, muscle tone, and heart rate as well as the amount of amniotic fluid to determine fetal well-being. The BPP includes an ultrasound test and a non-stress test.