Common Prenatal Tests
Tests are used during pregnancy to check your and your baby's health. At your fist prenatal visit, your doctor will confirm your pregnancy with a pregnancy test. The doctor will perform some tests to see if you or your baby could be at risk for any health problems. The doctor will also check for the following things:
- Your blood type and Rh factor
- Infections, such as toxoplasmosis and sexually transmitted infections (STIs), including hepatitis B, syphilis, chlamydia, and HIV
- Signs that you are immune to rubella (German measles) and chicken pox
Throughout your pregnancy, the prenatal care doctor may also recommend several other tests. Some tests, such as screening for gestational diabetes, Down’s syndrome, and HIV are suggested for all women. The prenatal doctor may recommend some other tests based on your:
- Personal or family health history
- Ethnic background
- Results of routine tests
Some tests are screening tests. They detect risks for or signs of possible health problems in you or your baby. Based on screening test results, your prenatal care doctor may recommend diagnostic tests. Diagnostic tests confirm or rule out health problems in you or your baby.
Common Prenatal Tests
Amniocentesis: A thin needle is used to draw out a small amount of amniotic fluid and cells from the sac surrounding the fetus. The sample is sent to a lab for testing.
This test is done at 14 to 20 weeks to help diagnose certain birth defects, including:
- Down’s syndrome
- Cystic fibrosis
- Spina bifida
This test is usually suggested for couples at higher risk for genetic disorders. It also provides DNA for paternity testing.
Biophysical profile (BPP): BPP involves an ultrasound exam along with a non-stress test. The BPP looks at the baby's breathing, movement, muscle tone, heart rate, and the amount of amniotic fluid.
This test is done in third trimester to monitor the overall health of the baby and to help decide if the baby should be delivered early.
Chorionic villus sampling (CVS): A needle removes a small sample of cells from the placenta to be tested.
This test is done at 10 to 13 weeks to diagnose certain birth defects, including:
Chromosomal disorders, including Down syndrome
Genetic disorders, such as cystic fibrosis
CVS may be suggested for couples at higher risk for genetic disorders. It also provides DNA for paternity testing.
First trimester screen: This test involves both a blood test and an ultrasound exam called nuchal translucency screening. The blood test measures the levels of certain substances in the mother's blood. The ultrasound exam measures the thickness at the back of the baby's neck. This information, combined with the mother's age, help doctors determine risk to the fetus.
This screening test done at 11 to 14 weeks to detect higher risk of:
Chromosomal disorders, including Down syndrome and trisomy 18
Other problems, such as heart defects
It also can reveal multiple births. Based on test results, your doctor may suggest other tests to diagnose a disorder.
Glucose challenge screening: First, you consume a special sugary drink from your doctor. A blood sample is taken one hour later to look for high blood sugar levels.
This screening test is done at 26 to 28 weeks to determine the mother's risk of gestational diabetes. Based on test results, your doctor may suggest a glucose tolerance test.
Glucose tolerance test: Your doctor will tell you what to eat a few days before the test. Then, you cannot eat or drink anything but sips of water for 14 hours before the test. Your blood is drawn to test your "fasting blood glucose level." Then, you will consume a sugary drink. Your blood will be tested every hour for three hours to see how well your body processes sugar.
This test is done at 26 to 28 weeks to diagnose gestational diabetes.
Group B streptococcus infection: A swab is used to take cells from your vagina and rectum to be tested.
This test is done at 36 to 37 weeks to look for bacteria that can cause pneumonia or serious infection in newborn.
Maternal serum screen: 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 in the mother's blood.
This screening test is done at 15 to 20 weeks to detect higher risk of:
Chromosomal disorders, including Down’s syndrome and trisomy 18
Neural tube defects, such as spina bifida
Based on test results, your doctor may suggest other tests to diagnose a disorder.
Non-stress test (NST): A belt is placed around the mother's belly to measure the baby's heart rate in response to its own movements.
This test is performed after 28 weeks to monitor your baby's health. It can show signs of fetal distress, such as your baby not getting enough oxygen.
Ultrasound exam: Ultrasound uses sound waves to create a "picture" of your baby on a monitor. With a standard ultrasound, a gel is spread on your abdomen. A special tool is moved over your abdomen, which allows your doctor and you to view the baby on a monitor.
An ultrasound exam can be performed at any point during the pregnancy. Ultrasound exams are not routine. But it is not uncommon for women to have a standard ultrasound exam between 18 and 20 weeks to look for signs of problems with the baby's organs and body systems and confirm the age of the fetus and proper growth. It also might be able to tell the sex of your baby.
Ultrasound exam is also used as part of the first trimester screen and biophysical profile (BPP).
Based on exam results, your doctor may suggest other tests or other types of ultrasound to help detect a problem.
Urine test: You will collect a small sample of clean, midstream urine in a sterile plastic cup. Testing strips that look for certain substances in your urine are dipped in the sample. The sample also can be looked at under a microscope.
This test is done to look for signs of health problems, such as:
Urinary tract infection
If your doctor suspects a problem, the sample might be sent to a lab for more in-depth testing.
Learning About Prenatal Tests and Their Results
If your prenatal care doctor recommends certain prenatal tests, ask him/her whey they are done and what the test results could mean. This can help you cope with any worries or fears you might have. Screening tests just evaluate risk for certain problems, they do not diagnose problems. If a screening test results is abnormal, it doesn't mean there is a problem with your baby. Request your doctor to explain what test results mean and possible next steps.