Every expectant mother wants a healthy baby. One way to help ensure this is through good prenatal care, including routine blood tests. Routine prenatal blood tests check the health of the mother during pregnancy, allowing for treatments that will prevent damage to her health and the health of her unborn child.
Routine Prenatal Blood Tests
Most of the routine blood tests will be done on your first prenatal checkup. Some will be repeated during additional prenatal care appointments to ensure the pregnancy is going smoothly. Other than the slight pain, and possible bruising, due to the needle prick, all of these prenatal blood tests are safe and do not present a risk to the fetus.
Blood type and Rh factor – A prenatal blood test will be performed to discover the blood type of the mother and if she is Rh-positive or Rh-negative.
The Rh factor is a protein found on the covering of red blood cells of some people. 85% of people are Rh-positive, meaning they have the Rhesus (Rh) protein. The 15% who do not carry the protein in their blood are Rh-negative. Having or not having the protein does not cause a physical issue until a pregnancy is involved. The baby of an Rh-negative woman can inherit the Rh-positive trait from its father. If the blood of the mother and baby mix at some point during the pregnancy, which is common, the mother’s blood may develop antibodies to the blood of the baby. This is similar to an allergic reaction. The antibodies in the mother’s blood can cross the placenta and attack the baby’s blood. This can lead to the baby developing anemia, brain damage or even death.
A medication called immunoglobulin (Rhlg) may be given to a mother with Rh-negative blood to prevent the formation of antibodies. This is commonly done during the 28th week of pregnancy. She will most likely receive an additional treatment of Rhlg after delivery to prevent problems during future pregnancies.
Anemia – Prenatal blood tests will be done to test your iron and hemoglobin levels. Low levels on either test can mean you either have or are at risk for anemia. Anemia during pregnancy will cause a woman to feel extremely fatigued and weak. It can also lead to a premature birth and low birth weight for the baby.
If your prenatal blood test results show anemia or a risk for anemia, your doctor may give you iron supplements or injections to bring you back into normal range.
Glucose Levels – A prenatal blood test will be performed to check your glucose (blood sugar) levels. Blood sugar levels that are above normal are a sign you may have, or are at risk for developing, gestational diabetes. The test is done between the 24th and 28th weeks in most women. Women who are at high risk for developing gestational diabetes will be tested earlier in their pregnancy.
Uncontrolled gestational diabetes can cause birth defects, including defects of the heart and spinal cord, as well as newborn complications, such as jaundice and breathing problems. It also increases the risk of premature delivery and stillbirth. Women with gestational diabetes are at risk for having extra large babies, weighing 10 pounds or more, leading to a difficult delivery or the need for a cesarean birth.
If your glucose levels show you have or are at risk for gestational diabetes, further tests will be ordered to determine the extent of the problem. Treatment consists of dietary restrictions and exercise. Some women may require the use of insulin or diabetic medications to fully control their blood sugar.
Rubella – A prenatal blood test will be done to test for immunity to Rubella (German measles). Becoming infected with Rubella during pregnancy can cause birth defects in unborn children. Common birth defects due to the disease include blindness, hearing impairment, heart defects, and mental retardation. It can also lead to miscarriage or stillbirth.
If the prenatal blood test shows you are not immune to Rubella, you will need to avoid exposure to the disease during your pregnancy. Rubella is rare in the United States due to childhood vaccinations, but your risk of infection increases if you are in crowds where visitors from countries who do not vaccinate for Rubella are present or if you plan to travel internationally during your pregnancy.
Sexually transmitted diseases – Sexually transmitted diseases can be passed from mother to unborn child during pregnancy and delivery. Prenatal blood tests for Hepatitis B and Syphilis are routine and you will be offered a test for HIV (human immunodeficiency virus) at the same time. Hepatitis B can cause extreme liver damage and death in babies. Syphilis can cause blindness, brain damage and death. HIV attacks the immune system and leads to AIDS (acquired immune deficiency syndrome).
If you are found to have Hepatitis B, your delivered baby will be treated with hepatitis B immune globulin (HBIG) and several injections of the Hepatitis B vaccine. Treatment for the mother also consists of the vaccine and HBIG, which are considered safe for use during pregnancy.
Syphilis is treated during pregnancy with a single penicillin injection when the disease has been present for less than one year, or with a longer dose of antibiotics if the infection is more severe.
Medications for HIV given during pregnancy will reduce the risk of passing the virus to your baby.
Toxoplasmosis – A prenatal blood test will be done to check for toxoplasmosis. Toxoplasmosis is a blood infection caused by a parasite transmitted by cats or through eating undercooked meat. The infection may not produce symptoms in the mother, but can cause severe complications when passed to the fetus. It can cause low birth weight, retinal abnormalities, brain calcification, mental retardation, and premature birth.
If the prenatal blood test is positive for toxoplasmosis, antibiotics will be prescribed to prevent damage to the unborn baby.
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Sources:
American College of Obstetricians and Gynecologists
American Pregnancy Association
March of Dimes
