Routine Tests Performed in Pregnancy

Reviewed by James Brann, MD
When pregnant, there are a number of different lab tests that doctors recommend women undergo during their routine prenatal care. These tests are used to help discover any conditions which may increase your risk of complications during pregnancy, or risk of complications regarding your unborn child.

Common tests during early pregnancy

Early on in your pregnancy, you should expect a number of different tests. These include:
  • Blood typing - This type of test shows the Rh factor. This is the type of protein found on red blood cells. While most people do have the Rh factor, it means they are Rh positive. If you don’t have the Rh factor, you are Rh negative. The problem comes when your unborn child is Rh positive and you are Rh negative. In this case, your body may actually make antibodies that work against the Rh factor. These types of antibodies may damage an unborn child’s red blood cells in a future pregnancy.
  • Complete blood count, or CBC - This type of test discovers the number of types of cells in your blood. Counting red blood cells can help determine whether you have a type of anemia. Counting white blood cells can help determine the number of disease-fighting cells you have. Counting the number of platelets can show if there’s a problem concerning blood clotting.
  • Urine culture - This type of test looks for bacteria. The presence of it may signal a urinary tract infection.
  • Urinalysis - This type of test looks for red blood cells to find out if you have a urinary tract disease. It also looks for white blood cells to find out if you have a urinary tract infection. Finally, it looks for glucose because high levels of it could signal diabetes. In addition, the test also measures protein. The level found in early pregnancy may later be compared with your levels later on in your pregnancy. A high level of protein in your urine may signal preeclampsia. This is a serious problem that normally happens either in late pregnancy or even after giving birth.
  • Hepatitis C and hepatitis B - Both hepatitis C and B are viruses which infect your liver. If a pregnant woman has either one she can pass the virus along to her baby. Every pregnant woman is tested for hepatitis B. If it turns out you have risk factors, your doctor may also want to test you for hepatitis C.
  • Human immunodeficiency virus, or HIV - This type of test is for all women. If a woman has HIV, she can still pass it on to her unborn child. In the case of HIV, it attacks your body’s immune system cells, causing acquired immunodeficiency syndrome, also known as AIDS. If you are infected, and you’re pregnant, you’ll be given medication. You’ll also be advised of certain other steps you can take to help reduce the chance you’ll pass it along to your unborn child.
  • Sexually transmitted diseases, or STDs - Every pregnant woman will be tested for both chlamydia and syphilis early on in her pregnancy. Both can lead to serious complications for a pregnant woman and her child. If either test comes up positive, you’ll be treated, and then tested again. Those with risk factors for gonorrhea will also be tested for it. Risk factors for gonorrhea include living in an area where it is common or a woman is age 25 or younger.
  • Tuberculosis, or TB - Only women who are at a high risk of TB need to be tested. This includes women infected with HIV, and those who live close to someone with TB.
  • Rubella - Also called German measles, rubella may cause birth defects if a woman becomes infected during her pregnancy. This type of test looks at your blood to find out if you’ve ever been infected with rubella, and if you’ve been vaccinated against it. If you’ve never had rubella and you haven’t been vaccinated, you need to avoid someone who has it during your pregnancy. Rubella is very contagious. If you’ve never been vaccinated, you’ll want to get the vaccine after you deliver. This rings true even if you choose to breastfeed. You don’t want to be vaccinated against rubella while you’re pregnant, though.

Common tests during later pregnancy

There are also a number of tests, which may be performed later on in pregnancy. They include:
  • Rh antibody - If you end up Rh negative, your blood is tested between weeks 28-29 of pregnancy for Rh antibodies. If it turns out you don’t have Rh antibodies, you will then receive Rh immunoglobulin. This type of shot will prevent you from then making antibodies later on in your pregnancy. You may need to have special care if you have Rh antibodies.
  • Group B streptococci, or GBS - This type of bacteria is found in your rectum and vagina. While many women who carry GBS don’t have symptoms themselves, they may still pass it on to their child during birth. Many babies who get GBS from their moms don’t have any problems, but some will get sick. This type of illness may lead to death in a newborn, or other serious health problems. Usually, GBS is found during a routine test between weeks 35-37 of your pregnancy. A swab is used to take a sample from your rectum and vagina. If the test is positive, you’ll be given antibiotics during your labor to help keep your baby safe from infection.
  • Repeat CBC for anemia
  • Glucose screening - This test determines the amount of glucose, or sugar, that’s in your blood. If you have high glucose, it could signal gestational diabetes. This type of test is common between weeks 24-28 of your pregnancy. If you have any diabetes risk factors, or if you had gestational diabetes during a previous pregnancy, screening could be done during your first trimester.

Birth defect screening tests vs. diagnostic tests

When it comes to testing for birth defects, a screening test is done to help find out the risk your baby has of common birth defects. This type of test, though, can’t tell you whether you baby has a birth defect. A screening test poses no risk to your unborn child.

On the other hand, a diagnostic test can detect many birth defects, which are caused by defects in either chromosomes or a gene. Your doctor may want you to do a diagnostic test if you have a history in your family of a birth defect, if you are a member of a certain ethnic group, of if you have another child already who has a birth defect. All pregnant women have the choice of doing a diagnostic test first, though, even if you don’t have any risk factors. It should be noted, some of these tests do carry a risk, including a small one for loss of pregnancy.
The first step in screening is determining our risk factors. Early on, your doctor may ask you some questions, including about your family history, ethnic background, if you’re age 35 or older, or if you have preexisting diabetes. You may want to also talk to a genetic counselor for more information.
  • Carrier test - In a carrier test, you and our partner will be tested to see if you carry the gene that causes a disorder, such as the case of cystic fibrosis. You can do a carrier test either before you get pregnant or during pregnancy. It’s usually recommended if you or your partner has a genetic disorder, if you have a family history of certain genetic disorders, if you already have a child with a genetic disorder, or if you’re in a certain ethnic group at a greater risk. Because it’s one of the most commonly inherited disorders, cystic fibrosis carrier screening is available to all women of childbearing age.
  • Ultrasound - Other screening tests include using an ultrasound, along with blood tests, to measure levels of certain types of substances in a mother’s blood.

Diagnostic tests include:
  • Chorionic villus sampling
  • Amniocentesis
  • Targeted ultrasound

The choice of whether to be tested for birth defects is up to you. If you find out during pregnancy that a test is positive, it gives you the option of ending your pregnancy. It may also give you time to learn more about the disorder, and line up the medical experts you need for the future. You should lean on your doctor, or contact a genetic counselor, to help you understand the options and make a decision.

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