Prenatal Care

Studies suggest that the risk of an increase in birth defects from x-rays performed during pregnancy is low. There is a slight increase in risk of childhood leukemia, which rises from approximately 2 in 6,000 cases to 3 in 6,000. This is a very small risk when compared to that of a newborn whose sibling has leukemia, where the risk is 1 in 720.

Your doctor will usually avoid ordering x-rays during pregnancy unless they are necessary for your health or for an emergency. The risk of birth defects increases after the exposure of radiation absorbed by the body rises from 5 - 10 rads (most will not expose the fetus to this level of radiaton). If it is not urgent, the x-ray will be postponed until after your pregnancy.

Magnetic Resonance Imaging (MRI) does not pose harm to the fetus, since it uses a magnetic field instead of ionizing radiation to create the image.

The AFP test measures the amount of alphafetaprotein in the blood. A certain amount is normal in all pregnant women. It is produced by your baby's liver, and passes through the placenta into your bloodstream.
Excessive amounts of AFP may indicate a neural tube defect such as anencephaly or spina bifida. An unusually low amount may indicate the presence of Down's syndrom in the baby.

Most doctors perform the AFP test between weeks 15 and 20. The most accurate results are obtained between weeks 16 and 18.

The risk of a neural tube defect is about 1 or 2 for every 1,000 pregnancies (0.1%-0.2%). The test returns a high positive value in 5 out of 100 pregnancies (5%). A high value will indicate the need for additional tests. You may be further along in your pregnancy that you previously thought, or you may be carrying twins.
AFP tests will detect all cases of anencephaly. It will also detect 80% of spina bifida cases.

AFP testing only detects about 20% of Down's syndrome babies.

The AFP3 detects neural tube defects in the same way as the regular AFP test, but it also measures three markers that help increase the ability to test for Down's syndrome.

In addition to measure the levels of alphafetaprotein in the bloodstream, the AFP3 test also measure the levels of human chorionic gonadotropin (HCG) and unconjugated estriol.
HCG is present in every pregnancy, and is used to determine whether you are pregnant (remember your home pregnancy test?). HCG is created by the placenta, and abnormally high values have been seen in Down's syndrome pregnancies.
Unconjugated estriol is a hormone that is synthesized by your baby's liver, the placenta and the adrenal glands. Unusually low levels have been found in Down's syndrome pregnancies. Low levels are also found in other pregnancies with a high somatic chromosome count.

Most positive tests are the results of normal variations in the bloodstream. The progression of your pregnancy may be more advanced than previously thought, or you may be carrying multiple babies.
The test may also reveal a Down's syndrome baby or other chromosomal abnormality, or suggest that your risk for carrying a Down's syndrome baby is increased for your age. Further testing is required.