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:

Which tests are done on all pregnant women
Why and when tests are done
What other tests may be needed

Initial Lab Tests

Some tests are given to all pregnant women. Other tests may be offered to you to help detect any problems.

A 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

Blood tests check for a number of things:

Blood type and antibody screen - Your blood type could 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 called Rh positive. Problems can arise when the fetus'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 will make antibodies that attack the fetus's blood. This can cause anemia (low iron levels). It will require special care during pregnancy.
Hematocrit and hemoglobin - The hematocrit and hemoglobin levels in your blood are measured to check for anemia.
Syphilis - Syphilis is an STD. Syphilis can be treated. If you have syphilis and are not treated, you could pass it to your baby.
Rubella - Your blood will be checked for signs of past German measles (rubella). If you had this condition before, you are not likely to get it again. If you haven't had it, while you are pregnant you should avoid anyone who has the disease. Vaccines for the disease are available, but it is best not to give them during pregnancy. If your blood test shows you are not immune to rubella, you should get the vaccine after the baby is born.
Hepatitis B virus - Hepatitis B infects the liver. If you have this infection, you can pass it to your baby. A drug called hepatitis B immune globulin may be given to help treat the illness. Your baby will be given the same medication and a vaccine against the disease after birth.
Human immunodeficiency virus (HIV) - HIV is the virus that causes AIDS (acquired immunodeficiency syndrome). Pregnant women are tested even if they do not have special risk factors. Your doctor will tell you that you are being tested for HIV. The test results will be explained to you. If you have HIV, there is a chance you can pass it to your baby. You can be given medication during pregnancy to reduce this risk.

For the Pap test, a speculum is inserted into the vagina. A small sample of cells is collected with a small brush or swab and scraper. The brush or swab is inserted into the cervical canal to reach the higher cells.

Urine test

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.

Cervical test

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 test

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.

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

Ultrasound

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.

Finally...

Some tests are given to all pregnant women. Other tests may be offered to you to help detect any problems. Whether to have further testing is up to you. If results of your screening test show there could be a problem, don't be alarmed. Treatment is now available for many problems that may occur during pregnancy. Keep in mind that most babies are born healthy.

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.

Chlamydia: A sexually transmitted disease that can cause pelvic inflammatory disease, infertility, and problems during pregnancy.

Down Syndrome: A genetic disorder caused by the presence of an extra chromosome and characterized by mental retardation, abnormal features of the face, and medical problems such as heart defects.

Estriol: A hormone made by the placenta and the fetal liver.

Gonorrhea: A sexually transmitted disease that may lead to pelvic inflammatory disease, infertility, and arthritis.

Hepatitis B Virus: A virus that attacks and damages the liver, causing inflammation, cirrhosis, and chronic hepatitis that can lead to cancer.

Human Chorionic Gonadotropin (hCG): A hormone produced during pregnancy; its detection is the basis for most pregnancy tests.

Human Immunodeficiency Virus (HIV): A virus that attacks certain cells of the body's immune system and causes acquired immunodeficiency syndrome (AIDS).

Maternal Serum Screening Tests: A group of blood tests that check for substances linked with certain birth defects.

Neural Tube Defects (NTDs): Birth defects that result from improper 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 Disease (STD): A disease that is 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.