Routine Tests During Pregnancy
During pregnancy, certain lab tests are done on all women. These tests can help your doctor spot possible problems during your pregnancy. They also will give clues to how your baby is doing. Other tests you have depend on your medical history, family background, ethnic background or exam results.
This pamphlet will tell you more about:
Initial Lab Tests
number of lab tests are recommended for all women early in prenatal care. Some of these tests are done to diagnose certain problems during your pregnancy. They are called diagnostic tests. Diagnostic tests may be offered based on your medical history, family background or previous test results. Sometimes your ethnic background may create a need for you to be tested for problems that occur more often in your ethnic group.
Other tests do not diagnose problems - they are done to see if you or your baby is at risk of certain problems or birth defects. These are called screening tests.
Lab tests done on all women include samples from your blood, urine and cervix. You also will be tested for certain infections, such as sexually transmitted diseases (STDs). The results of these tests are used to find out if there are any problems. If problems are found, many of them can be treated during pregnancy.
Some of these tests will be done more than once. The results will be noted in your medical record. If you have concerns about any of these tests, talk to your doctor.
No test is perfect. There may be a problem even if the test does not show it. Also, the problem may not exist even if the test does show it. Your fetus also may have a problem that the test was not designed to find.
Blood tests check for a number of things:
Your urine will be tested at each prenatal visit. This test checks the levels of sugar and protein. Often, sugar in the urine is normal in pregnancy. High levels of sugar could be a sign of diabetes. Protein in the urine may be a sign of urinary tract infection, kidney disease or high blood pressure that occurs in late pregnancy. The urine test also is used to check for infections of the bladder and kidneys. If these problems occur, they can be treated.
A Pap test may be done to check for changes of the cervix that could lead to cancer. A sample may be taken from your cervix to check for certain STDs, such as gonorrhea and chlamydia. If any of these conditions are found, they can be treated.
Maternal Serum Screening Tests
Maternal serum screening tests are used to find out if you have a higher-than-normal risk of having a baby with certain birth defects. These tests measure the level of certain substances in your blood. The levels may be higher or lower than normal if your fetus has certain defects.
The two most common screening tests are alpha-fetoprotein (AFP) and multiple marker screening. In most cases, they are done between 15 weeks and 18 weeks of pregnancy. Neither test poses a risk to the mother or fetus.
Alpha-fetoprotein is a protein made by the fetus. It is present in fetal blood and in amniotic fluid (liquid that surrounds the fetus in the mother's uterus). A small amount of AFP crosses the placenta and enters your blood.
A small amount of blood is taken from a vein in your arm and tested in a lab. Results come back in about a week. A high level of AFP can signal a risk of neural tube defects (such as spina bifida). A low level can signal a risk of Down syndrome.
Positive results don't always mean there's a problem. For this reason, an abnormal screening test result is followed up with other tests.
Although they are not done on all women, you may be offered one or more of these tests during your pregnancy:
Amniocentesis - a procedure in which a small amount of amniotic fluid and cells are taken from the sac surrounding the fetus and tested.
Chorionic Villus Sampling (CVS) - a procedure in which a small sample of cells is taken from the placenta and tested.
Genetic Tests - screening and diagnostic tests that often can show whether the fetus has certain birth defects. Some genetic tests are offered to all pregnant women. Others may be offered if your medical history, family history, age or physical exam raise questions about your baby's health.
Glucose Screening - to test for diabetes, the patient drinks a special sugar mixture. An hour later, a blood sample is drawn from her arm and sent to a lab. There, a technician measures the level of glucose in the blood.
Group B Streptococcus (GBS) - to test for GBS, samples are taken from the vagina, perineum and rectum and grown in a special substance. A urine sample also may be used.
Tuberculosis - a simple skin test can check for tuberculosis even before symptoms occur.
Ultrasound - a test in which sound waves are used to examine internal structures, including the fetus.
Multiple marker screening
Multiple marker screening measures the levels of the hormones estriol and human chorionic gonadotropin (hCG), as well as AFP, in your blood.
This test can be done at the same time, using the same blood sample, as the AFP test. The results come back in 1 week to 2 weeks. If a fetus has Down syndrome, hCG levels often are higher than normal. Estriol levels and AFP often are lower than normal.
Routine tests can be followed up with other tests if the results raise concerns. Your doctor also may suggest special tests if you have certain risk factors
An ultrasound exam is a test that creates an image of your fetus from sound waves. This is done by moving a device (called a transducer) across your abdomen or placing a special device in your vagina.
An ultrasound exam may be done on women whose doctors want to know the age of the fetus, confirm a diagnosis, or check what may be a problem. It can be done any time during pregnancy.