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Prenatal Tests

Prenatal tests are routinely ordered during pregnancy to monitor the health of you and your baby.

At your fist prenatal visit, your doctor will recommend tests to evaluate a number of things, including:

Throughout your pregnancy, your health care provider may suggest a number of additional tests Some tests are suggested for all women, such as screenings for gestational diabetes, Down syndrome, and HIV.

Other tests might be ordered based on your:

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 doctor might suggest diagnostic tests. Diagnostic tests confirm or rule out health problems in you or your baby.

The following chart describes some of the most common prenatal tests:

Test What It Is How It Is Done
Amniocentesis (AM-nee-oh-sen-TEE-suhss)

This test can diagnosis certain birth defects, including:

  • Down syndrome
  • Cystic fibrosis
  • Spina bifida

It is usually performed at 14 to 20 weeks.

It may be suggested for couples at higher risk for genetic disorders. It also provides DNA for paternity testing.

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.

Biophysical profile (BPP)

This test is used in the third trimester to monitor the overall health of the baby and to help decide if the baby should be delivered early.

BPP involves an ultrasound exam along with a nonstress test. The BPP looks at the baby's breathing, movement, muscle tone, heart rate, and the amount of amniotic fluid.

Chorionic villus sampling (CVS)

A test 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.

A needle removes a small sample of cells from the placenta to be tested.
First trimester screen

A 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.

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.

Glucose challenge screening

A screening test done at 26 to 28 weeks to determine the mother's risk of gestational diabetes.

Based on test results, your doctor may suggest a blood glucose test or a glucose tolerance test

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.
Glucose tolerance test

This test is done at 26 to 28 weeks to diagnose gestational diabetes.

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.

Group B streptococcus infection

This test is done at 36 to 37 weeks to look for group B strep (GBS) bacteria that can cause pneumonia or serious infection in newborn.

A swab is used to take cells from your vagina and rectum to be tested.

Maternal serum screen (also called quad screen, triple test, triple screen, multiple marker screen, or AFP)

A screening test done at 15 to 20 weeks to detect higher risk of:

  • Chromosomal disorders, including Down 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.

Blood is drawn to measure the levels of certain substances in the mother's blood.

Nonstress test (NST)

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.

A belt is placed around the mother's belly to measure the baby's heart rate in response to its own movements.

Ultrasound exam

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.

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.

Urine test

A urine sample can look for signs of health problems, such as:

  • Urinary tract infection
  • Diabetes
  • Preeclampsia

If your doctor suspects a problem, the sample might be sent to a lab for more in-depth testing.

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.

Understanding Prenatal Tests and Test Results

If your doctor suggests certain prenatal tests, don't be afraid to ask lots of questions.

Learning about the test, why your doctor is suggesting it for you, and what the test results could mean can help you cope with any worries or fears you might have.

Keep in mind that screening tests only evaluate the likelihood of there being a problem. Abnormal screening test results alone do not mean that there is a problem with your baby. If a screening test comes back abnormal, the screening test may be reordered or additional tests may be recommended.

Your doctor can explain what test results mean and possible next steps.

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Reference: CDC