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An Introduction to Prenatal Testing

These screenings and diagnostics can check for common problems.

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Prenatal tests can tell a lot about the health of you and your unborn baby. Tests are done throughout pregnancy. Many tests are given to almost all pregnant women as part of their prenatal care. Other tests are suggested to certain women by their doctors based on any risk factors they may have.

Common risk factors during pregnancy include:

  • A family history of genetic or birth defects
  • A mother with diabetes, high blood pressure, HIV or other health conditions
  • Previous pregnancy complications, miscarriages or stillbirths
  • A pregnancy with multiples (twins, triplets or more)
  • Exposure to something harmful during pregnancy (radiation, chemicals or certain drugs including tobacco and alcohol)
  • Screening tests that show abnormal results
  • A mother who is 35 or older
  • A mother who is underweight
  • A mother who is overweight

Your blood and urine will be tested at your first doctor’s visit. This is to confirm your pregnancy and to check for blood problems or  signs of  infections. These infections could pass to the baby. Expect to have your urine tested and blood pressure taken at each visit. These are easy ways for your doctor to identify any problems.

Routine prenatal tests can show if you have:

  • Gestational diabetes
  • Anemia
  • Immunity to certain diseases, such as chicken pox and rubella
  • Infections, such as STDs, hepatitis B,  or urinary tract infections
  • Rh incompatibility (your blood type is different from your baby’s blood type)

It’s important to find and treat these conditions early to keep you and your baby healthy.

Screening tests can tell if you’re at risk of having a baby with a genetic disorder or birth defect. These are usually offered in the first and second trimester. Screening tests include ultrasound and blood tests. They can check for conditions like Down syndrome and trisomy 18. You can also have a test to see if your baby is at risk for neural tube defects.

Depending on the initial test results, your doctor may suggest diagnostic testing. These tests confirm or rule out genetic disorders or birth defects in your baby. They include amniocentesis and chorionic villus sampling (CVS).

  • Amniocentesis is usually done between weeks 15 and 20 of pregnancy. A sample of amniotic fluid is taken and analyzed. Lab results are ready in two weeks.
  • Chorionic villus sampling (CVS) can be done earlier, between weeks 10 and 12 of pregnancy. The doctor takes a sample of tissue from the placenta and the laboratory examines it. Lab results are ready in about one week.

These tests are not risk-free. There is a slight risk of miscarriage as a result of amniocentesis or CVS.

Some discomfort is common during pregnancy. This includes nausea, back pain and fatigue. If you’re not sure what’s normal, call your doctor or midwife. 

By Susan Warner, Contributing Writer

American College of Obstetricians and Gynecologists. Your Pregnancy and Childbirth: Month to Month. 6th ed. Washington, DC: ACOG; 2015.
American College of Obstetricians and Gynecologists. Routine tests in pregnancy. Accessed: June 30, 2016.
Medline Plus. Prenatal testing. Accessed: June 30, 2016.
Medline Plus. Health problems in pregnancy. Accessed: June 30, 2016.

Last Updated: June 30, 2016