What Doctors Look For When They Draw Expectant Moms Blood Samples

What do you do after a positive home pregnancy test? You will call your doctor and get a blood test done. This test will tell you how much of the pregnancy hormone, HCG, is in your blood and approximately how far along you are. This hormone starts to circulate your body once the embryo has implanted in the uterus. It is actually the fertilized egg that secretes HCG. This hormone stimulates the cyst on the ovary, the corpus luteum, to produce more progesterone, which will maintain the pregnancy. This hCG/progesterone system sticks around till about 12-14 weeks until the placenta is fully functional and takes over progesterone production. At that point the cyst goes away and HCG levels drop and aren't needed.

Many doctors do a quantitative blood test to measure the exact amount of HCG present and make sure it is doubling every 2-3 days. If it isn't, then there might be complication or the pregnancy might be in danger. You might have several of these blood tests done in the first 2-3 weeks to make sure all is good. Some doctors don't bother to do a quantitative test and just do a yes or no confirmation blood test, the qualitative test. It basically says the same thing as a home urine test. If there is more than 5 mIU of HCG in the blood then a yes will come back from the lab.

Once the pregnancy has been confirmed you will come in for your first appointment at approximately 6-8 weeks along. You will get an estimated due date (EDD) and have a series of tests done. Besides the normal blood pressure, temperature, and urine protein test, you will have a huge blood draw at this time. A complete series of tests will be performed on this blood to rule out many possible complications. Here is a list of the tests that will be run on your blood at this time.

â—� a complete blood cell count (CBC).

â—� Blood typing and screening for Rh antibodies.

â—� for syphilis, hepatitis, gonorrhea, chlamydia, and other sexually transmitted

diseases (STDs), including human immunodeficiency virus (HIV).

â—� for evidence of previous exposure to chickenpox (varicella), measles (rubeola),

mumps, or German measles (rubella).

â—� for cystic fibrosis (this is a new one).

â—� for sickle cell trait or disease because they're at higher risk for having sickle-

cell anemia, if you are from African or Mediterranean origin.

Routine Visits and Testing

As long as your pregnancy is not high-risk, you will go to see your doctor once a month till you are 7 months along. At this point you will be seen twice a month to make sure there are no signs of early delivery or development of later pregnancy problems, such as high blood pressure or extreme edema. Once you hit your 9th month you will be seen weekly till your delivery. At different points in your pregnancy, you will have to give another blood sample to have gestational specific tests done. Some of these tests are optional and some are a must. You will be screened for gestational diabetes at 12 weeks if you are at high risk of having it. Women who have had a baby weighing over 9 lbs, a family history of diabetes, are 30 or older, or obese will be required to test at this point. All other women will be tested at 28 weeks. This test requires that you eat a huge carbohydrate breakfast or fast and drink a surgery drink. For the breakfast choice, you come in 1-2 hours later and have your blood draw. For the sugar drink, you come in and drink and wait an hour to have blood drawn. If the test comes back high for blood sugar than you are re-tested in 3 hours to see if you have gestational diabetes.

There are a wide variety of other prenatal blood tests that one can choose from. These can help predict the likelihood or presence of certain genetic or developmental diseases.

Alpha-fetoprotein screening (AFP) can be done between 16 and 18 weeks. The level of alpha-fetoprotein, a protein produced by the fetus, can be measured in the woman's blood. If the level is high, there is a higher chance she is carrying multiples, the baby has spinal bifida or other neural tube defects, or they are just high and nothing is wrong at all. If the level is low, this could indicate chromosomal issues like Downs Syndrome or other chromosomal anomalies. This test can tell you are at higher risk for certain issues but not that the outcome is certain. More tests will have to be performed to be sure.



Multiple marker screening (also called a maternal serum screening, triple screen, triple marker, quadruple screen, quad screen, quadruple marker, or quad marker): Also between 16 and 18 weeks, your doctor or midwife may measure the levels of certain hormones in your blood, along with AFP. For this screening, a sample of blood is drawn from the mother to measure the level of AFP, as well as the levels of HCG (human chorionic gonadotropin) and estriol, which are produced by the placenta. The levels of these three substances (which is why the test is often called the triple screen or triple marker) in the blood can help doctors identify a fetus at risk for certain birth defects or chromosomal abnormalities. The test is called a quadruple screen (or marker) when the level of an additional substance, called inhibin-A, is also measured.