Obstetrics - Prenatal care

 

Routine cultures and blood and urine tests

During pregnancy, certain routine lab tests are done on all women. Depending on your health history and the results of your routine tests, your obstetrician or midwife may recommend that you have other tests.

To confirm a pregnancy, your blood or urine may be tested for the hormone human chorionic gonadotropin (hCG). Also, the provider can order lab tests to check for any diseases or infections. These tests may include:

• Urine tests: A urine sample is checked to look for sugar, protein, and bacteria, which can signal diabetes or a bladder or kidney problem. This test is performed at every prenatal visit. Also, a urine specimen is sent for culture because bladder infections are very common in pregnancy.
• Routine blood tests: Blood samples are checked for anemia and certain infections. Your blood type and Rh factor also are noted.
• Hepatitis B blood test: A blood test can show whether someone has been infected with hepatitis B virus. For the test, a small sample of blood is taken and tested for a special protein—called an antigen—that is found in blood infected with the virus. If your test result is negative, it means you were not infected with the virus at the time the test was done. If your test result is positive, it means you have been infected with the virus and can infect others. This includes your baby if you are pregnant. Your doctor will want to do more tests to learn whether your liver is still healthy. A positive test result means that your children, your sexual partner(s), and others living in your household are at risk of infection. They should be told about testing and vaccination. They will need to decide whether to have them done.
• Pap test or cervical culture: The cells from the cervix collected during a pelvic exam may be checked for signs of infection, cancer, or conditions that could lead to cancer.
• Glucose screening test: The sugar level in the woman's blood is measured to test for gestational diabetes. Unless significant risk factors are identified early in pregnancy, this glucose tolerance test is performed at approximately 28 weeks of pregnancy.
• Group B beta streptococcus (GBBS) testing: A culture of a woman's vagina and rectum is tested for the presence of GBBS, which can be passed to the baby during delivery and cause serious infection.
• Human immunodeficiency virus (HIV) test: A blood sample is checked for HIV antibodies. If the test result is positive, another test is used to confirm the results. If you have HIV, you could pass it to your baby during pregnancy, labor, delivery, and breastfeeding. There are things you can do to help prevent this from happening.

Tests can be done to help detect certain birth defects. These tests are done at various times during pregnancy. Some may need to be done in a special center equipped to perform them.

Some tests are offered to all women to help assess the risk of certain birth defects. These screening tests do not diagnose birth defects, but they may tell if there is an increased risk for a problem. Types of screening tests include:

• First trimester screening: The result of a special ultrasound (nuchal translucency scan) is combined with a maternal blood test (also called "triple" or "quad" or “penta” screen) to determine your baby's risk for Down syndrome and trisomy 18. These tests are done between 10 and 14 weeks of pregnancy.
• Maternal serum screening: A maternal serum Alpha fetal protein (MSAFP) blood test that checks for abnormal levels of a substance that is linked to certain birth defects, such as Down syndrome and neural tube defects. This test is done between 15 and 20 weeks of pregnancy. Additional blood tests or ultrasound are added if the first trimester screening had not been done.
• Cystic fibrosis testing: A lab test done on a sample of blood or saliva to see if a couple is at an increased risk for giving birth to a child who will have cystic fibrosis. This test can be done before pregnancy or early in pregnancy.

Other tests are done if the results of a screening test or other factors raise concerns about your baby. The results of these tests often can show whether the fetus has certain birth defects:

 

No test is perfect. A test may not find a birth defect that is present, or your baby may have a problem that the test was not meant to find. The tests cannot find all birth defects.

 

If the results show that there is a problem, a counselor can help explain how the baby will be affected. In some cases, it is not known how severe a birth defect will be. Sometimes surgery or treatment is possible. In other cases, there is no treatment for a defect. The counselor and doctor can explain the results and provide guidance in making choices and considering options.

You and your obstetrician or midwife will discuss your results and decide what treatment and other tests, if any, are best for you.

 

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