Tests During Pregnancy

A number of lab tests are suggested for all women early in prenatal care, including samples from your blood, urine, and cervix. You also will be tested for 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 can be treated during pregnancy.

Some tests are done to see if you or your baby are at risk of certain problems or birth defects. These are called screening tests. They may be offered based on your age, history, or ethnic background.

Other tests are done to find problems that may occur during your pregnancy. These are called diagnostic tests. They may be offered based on your medical history, family background, or results of other tests. You also may want to be tested for problems that occur more often in your ethnic group.

Some tests will be done more than once. If you have concerns about any test, talk to your doctor. No test is perfect. There may be a problem even if a test does not show it. A problem may not exist even if a test does show it. Your baby also may have a problem that tests were not designed to find.

Blood Tests

All blood tests may not be done at the same appointment. Some may be done early in pregnancy and some may be done later in pregnancy. Blood tests are done to check for a number of things:

• Blood type and antibody screen. Your blood type can be A, B, AB, or O. It can be Rh positive or Rh negative. If your blood lacks the Rh antigen, it is Rh negative. If it has the antigen, it is Rh positive. Problems can arise when the baby's blood has the Rh factor and the mother's does not. The mother's body may react as if it were allergic to the fetus. It can make antibodies that attack the baby's blood. This can cause the baby to be anemic (have low iron levels) and requires special care during pregnancy.
• Hematocrit and hemoglobin. The levels of these two substances are measured to check for anemia. If low levels of iron are found, you may be given supplements to increase them.
• Rubella. Your blood will be checked for signs of a past infection with German measles (rubella). If you had this infection before, you are not likely to get it again. If you have not had it, while you are pregnant avoid anyone who has the disease. A vaccine for rubella is available, but it is best not to get it during pregnancy. If your blood test shows you are not immune, you should get the vaccine after the baby is born.
• Hepatitis B virus. This virus infects the liver. If you have it, you can pass it to your baby. After the baby is born, you may be given a drug to help treat the virus. Your baby will be given the same medication and a vaccine against the virus after birth.
• Syphilis. This STD can be treated. If you have it and are not treated, you could pass it to your baby. This disease can cause major health problems for a baby if he or she is infected.
• Human immunodeficiency virus (HIV). HIV is a virus that attacks certain cells of the body's immune system and causes AIDS (acquired immunodeficiency syndrome). If you have HIV, there is a chance you could pass it to your baby. While you are pregnant you can be given medication to help reduce this risk.
• Glucose. The level of sugar in your blood is measured to test for diabetes. Diabetes is a disease in which the body does not make enough insulin or does not use it as it should. For this test, you drink a special sugar mixture. An hour later, a blood sample is drawn from your arm and sent to a lab. This test usually is done later in pregnancy. In most cases, a special diet and exercise can help control diabetes. Medication also may be needed.

Your urine will be tested at each prenatal visit. This test checks the levels of sugar and protein. Although the presence of sugar in the urine is normal in pregnancy, high levels could be a sign of diabetes. Protein in the urine may be a sign of a 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.

Cervical Tests

A Pap test may be done to check for changes of the cervix that could lead to cancer. A sample also may be taken from your cervix to check for certain STDs, such as gonorrhea and chlamydial infection. If any of these conditions are found, they can be treated.

Late in pregnancy, you will be tested for group B streptococcus (GBS). For this test, a swab is used to take samples from your vagina and rectum. GBS can be passed to a baby during birth. If this occurs, it can cause problems in the first weeks of a baby's life. Antibiotics can be given during labor to help prevent the baby from being infected.

Testing for Birth Defects

Birth defects may affect the baby's health, or his or her ability to function. Some defects can be prevented, and many can be treated or corrected with medication or surgery.

Some birth defects are passed from parent to child. In many cases, the reason for a defect is not known.

Before or during pregnancy, some tests are offered to check the parents' risk for having a baby with certain defects. The results of these tests, along with genetic counseling, will let parents know about their risk of having a baby with a problem.

Near the end of the first trimester, screening tests for some birth defects may be offered. Maternal serum screening tests are used to find out if you are at increased risk for having a baby with certain birth defects:

• Neural tube defects
• Down syndrome
• Chromosome defects

These tests measure the level of three or four substances in your blood. The levels may be higher or lower than normal if your fetus has certain defects, such as neural tube defects or Down syndrome. These tests may be combined with the results of a special ultrasound test, called nuchal translucency screening, to show if there might be a defect. Maternal serum screening poses no risk to the mother or fetus.

A positive result does not always mean there is a defect. Sometimes it means there is a greater risk of one. A negative result does not always mean there is no defect. Many tests focus on finding only one kind of problem and other problems can be present.

If the results of screening show a risk, a diagnostic test may be done. Diagnostic tests may include:

• Amniocentesis. For this test, a small amount of amniotic fluid and cells are taken from the sac surrounding the fetus and tested.
• Chorionic Villus Sampling. For this test, a small sample of cells is taken from the placenta and tested.
• Ultrasound. This type of ultrasound exam gives a detailed view of the baby's organs and features.

Finally...

Some tests are given to all pregnant women to help detect problems that could pose a risk to the mother or the baby. Finding such problems early allows your doctor to treat them or to plan for any special care you may need. The goal of these tests is to help you have a healthy baby.

Glossary Antigen: A substance, such as an organism causing infection or a protein found on the surface of blood cells, that can induce an immune response and cause the production of an antibody. Cervix: The lower, narrow end of the uterus, which protrudes into the vagina. Chlamydial Infection: A sexually transmitted disease caused by bacteria that can lead to pelvic inflammatory disease and infertility. Chromosome: A structure that is located inside each cell in the body and contains the genes that determine a person's physical makeup. Down Syndrome: A genetic disorder in which mental retardation, abnormal features of the face, and medical problems such as heart defects occur. Gonorrhea: A sexually transmitted disease that may lead to pelvic inflammatory disease, infertility, and arthritis. Neural Tube Defects (NTDs): Birth defects that result from incomplete development of the brain, spinal cord, or their coverings. Pap Test: A test in which cells are taken from the cervix and vagina and examined under a microscope. Sexually Transmitted Diseases (STDs): Diseases that are spread by sexual contact, including chlamydial infection, gonorrhea, genital warts, herpes, syphilis, and infection with human immunodeficiency virus (HIV, the cause of acquired immunodeficiency syndrome [AIDS]). Syphilis: A sexually transmitted disease that is caused by an organism called Treponema pallidum; it may cause major health problems or death in its later stages.

This Patient Education Pamphlet was developed under the direction of the Committee on Patient Education of the American College of Obstetricians and Gynecologists. Designed as an aid to patients, it sets forth current information and opinions on subjects related to women's health. The average readability level of the series, based on the Fry formula, is grade 6–8. The Suitability Assessment of Materials (SAM) instrument rates the pamphlets as "superior." To ensure the information is current and accurate, the pamphlets are reviewed every 18 months. The information in this pamphlet does not dictate an exclusive course of treatment or procedure to be followed and should not be construed as excluding other acceptable methods of practice. Variations taking into account the needs of the individual patient, resources, and limitations unique to the institution or type of practice may be appropriate.

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