Common Prenatal Tests

During your monthly checkups, your caregiver will weigh you, check your blood pressure, and take a urine sample to test for sugar or protein in your urine (which can signal gestational diabetes or pregnancy-induced high blood pressure). Finally, he'll measure your abdomen to see if your baby is growing at the expected rate.

Your caregiver may also offer you a battery of prenatal tests now, including:

• Alpha-fetoprotein (AFP) or triple-marker screening - AFP is a substance produced by the fetus. It's present in your bloodstream and can be measured with a simple blood test. A triple-marker screening is similar to an AFP test, but provides more specific results because it also measures the hormones estriol and hCG. Abnormal levels of these substances can indicate an increased risk for problems such as neural tube defects or Down syndrome. The tests do not diagnose these conditions, however. If your screening test is abnormal, your caregiver will suggest additional tests, such as ultrasound and amniocentesis, to help determine why. (Read more... )
• Ultrasound - Using high-frequency sound waves, ultrasound creates a "picture" of your developing baby. It helps your caregiver pinpoint the fetus' age, detect multiple fetuses, and spot conditions such as neural tube defects. (Read more... )
• Amniocentesis - This procedure can detect or rule out disorders such as Down syndrome and neural tube defects. Guided by ultrasound, a doctor or medical technician inserts a long, hollow needle through your abdomen and into the amniotic sac. He then draws out a small sample of amniotic fluid. The sample is sent to a lab, where cells that have been sloughed off from the fetus are grown and analyzed for chromosomal defects. This test is generally offered only to women who have an increased risk for having a baby with genetic defects -- women over 35, for instance, or those with a family history of inherited disorders. (Read more... )
• Glucose tolerance testing - This test checks for signs of gestational diabetes. It's fairly straightforward: You drink a sweetened solution, and an hour later a blood sample is drawn and your blood sugar level is measured.
• Hemoglobin testing - This test measures the amount of red blood cells in your blood. Too few can indicate anemia, a common (and easily remedied) problem during pregnancy.

Common 1st Trimester Prenatal Tests

In the first trimester, you will probably receive a group of tests known in many health centers as the "prenatal panel." This panel of tests usually includes, but is not limited to, a complete blood count (CBC), blood typing (including Rh screen), rubella viral antigen screen, hepatitis panel, and urine analysis. Other tests may be obtained based on your health and previous pregnancy history.

An ultrasound may be obtained in the first trimester to determine the health of the pregnancy, usually as a result of signs or symptoms of miscarriage or an ectopic pregnancy (pregnancy outside the womb). Most diagnostic ultrasound exams occur in the second trimester.

For women at increased risk for chromosome and genetic diseases (those women who are 35 years old and older), advances in prenatal diagnosis now allow for detection of possible problems during the first trimester. A test called chorionic villus sampling (CVS) can detect Down syndrome and other genetic disorders as early as 10 weeks into a pregnancy. It is as safe and accurate as a second trimester amniocentesis. To determine which procedure is right for you, discuss the various options with your health-care provider, a genetics counselor, or a maternal-fetal specialist.

Common 2nd Trimester Prenatal Tests

The second trimester is an important time for the main screening tests to determine how you and your baby are doing. The first ultrasound (also called a sonograph) is typically done early in the second trimester, to check on your baby's health and age. The second ultrasound examination is usually done at the end of the second or the beginning of the third trimester. This one confirms the findings from the first ultrasound, and checks to see how the baby is developing.

Early in the second trimester is also a time for a blood test that can alert your health-care provider about any abnormalities the baby may have. The older version of this test only screened for fetal alpha-fetoprotein, a protein that is abnormally high in cases of neural tube defects. More modern versions of the tests also check hCG (human chorionic gonadotropin), estriol (placental estrogen), and alpha-fetoprotein. Abnormal test results signal that your baby might be at risk for genetic defects, diabetes, preterm labor, or other abnormalities. To confirm the blood test findings, you may be referred for a special ultrasound, or get an amniocentesis (a procedure for taking a sample of amniotic fluid to be tested).

Late in the second trimester, you are screened for diabetes, hepatitis B, retested for sexually transmitted infections, and may have a pelvic examination to detect whether your cervix is weak or dilating.

Common 3rd Trimester Prenatal Tests

Your health-care provider will perform the test that checks for beta-strep infection on the perineum. About 20% of all women may be carriers of this bacterium. It usually does not cause any illness for adults, except occasional urinary tract infections. We now know that beta-strep is the number one cause of newborn infection in those who develop sepsis (systemic infection). Women who test positive for beta-strep will receive intravenous antibiotics in labor.

In the third trimester it is still common for your health-care provider to perform cervical exams if you have signs of labor or if ruptured membranes are suspected. If it appears that the baby is not as active as expected, or if you have any high risk factors, your baby may be watched more closely. This is called fetal monitoring, and requires you to wear a belt that can electronically pick up the baby's heart rate and your uterine contractions. Ultrasounds are used to determine the baby's growth, or to detect abnormalities if they are suspected.

Review Date: June 29, 2001
Reviewed By: Peter Chen, M.D., Obstetrics and Gynecology, University of Pennsylvania School of Medicine. Review provided by VeriMed Healthcare Network.


The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2001 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.