Obstetrics, Gynecology and Infertility
4323 North Josey Lane
Plaza I, Suite #203
Carrollton, Texas 75010
972-394-7277 or www.DrCmd.com

This is a blood test for pregnant women which may detect certain birth defects in the unborn baby. The test may also give information about the likelihood of twins, incorrect dating of the pregnancy and the risk for some pregnancy complications.

This blood test evaluates the levels of three hormones: Alpha-fetoprotein (AFP), which is a protein made by developing babies, Human chorionic gonadotropin (HCG), which is the hormone of pregnancy that is detected in pregnancy tests and Estradiol (E2), which is the main female estrogen hormone.

The information gained from this test may be useful for managing your pregnancy. A normal test result means that it is unlikely that certain birth defects are present. If a birth defect is suspected or found, you will be able to make informed decisions about when, where and how to deliver your baby.

A positive test result means there is more or less than the usual amount of these hormones present in the pregnant woman's blood. In most cases a positive result does not mean that the baby has a birth defect. About one of every twenty tests will initially be positive and further testing will be needed. Remember, this is just a screening test and an abnormal result is only saying that the risk of the problem is increased, but it is not necessarily present.

An ultrasound examination to determine the age of the pregnancy and to look for structural birth defects may be recommended. An amniocentesis may also be recommended to do more definitive tests for a structural birth defect or a chromosome abnormality. Amniocentesis is a test in which a small amount of fluid is taken from the fluid which surrounds the baby.

Unfortunately, this test will not tell us about all types of birth defects or genetic abnormalities (i.e. sickle cell, cystic fibrosis, Tay Sach's disease, etc. are not detected). Some birth defects cannot be diagnosed until after a baby is born. The test also cannot detect every baby with spina bifida, since a small open spina bifida or one covered with skin may not cause an elevated test. The test will also not detect every baby with Down's syndrome.

The level of AFP in the mother's blood increases as the pregnancy progresses. The most common reason for an elevated test is inaccurate dating of the pregnancy, i.e. the pregnancy is actually further along than we thought. The presence of twins will also cause a high AFP because two babies produce more of the protein than one baby. Sometimes, high levels of AFP in the mother's blood are a clue that the pregnancy is at risk for other problems such as prematurity. Only rarely does an elevated test indicate that the baby has a birth defect.

The AFP component itself screens mostly for neural tube defects (present in about 1 to 2 out of every 1000 babies). The most severe form of neural tube defect is anencephaly, where much of the brain and skull fail to form. These babies are stillborn or die very soon after birth. In spina bifida, the spinal column does not close properly. The nerves in the exposed area are damaged as a result, causing weakness or paralysis of the legs, difficulty with bowel and bladder control and lack of sensation. The severity of these handicaps varies, depending on the size and location of the defect. Although surgical and medical treatment cannot cure spina bifida, many individuals are able to participate fully in school and life activities despite their disability. Test levels can also be high if the developing baby has an abnormal opening of the abdominal wall, for which immediate medical attention at birth is usually necessary. The outcome depends upon many factors including the type of abdominal wall defect.

The most common cause of a low test result is that the pregnancy is not as far along as originally thought. However, low levels are also associated with an increased risk for chromosome abnormalities including Down Syndrome. Individuals with Down's Syndrome typically have low I.Q.s and may have medical problems such as congenital heart defects.

If a birth defect is found, I or a genetic counselor will answer your questions about what this may mean for your baby and what options are available to you. Knowledge of the baby's problem may impact where, when and how you will deliver. It may alert me to the need for special medical care for the baby. Some couples may also elect to end a pregnancy that would start life with a significant disability. This is a hard situation when a problem is found.

The testing involves taking a blood sample between the 14th and 20th week of pregnancy (from the last menstrual period). The best time is between 14 and 17 weeks. Timing is important because unreliable results may be obtained if the sample is obtained too early or too late in the pregnancy.

Inform me of your decision to have this screening test and arrangements will be made to have your blood drawn