All pregnant women are now being offered maternal serum screening (also known as AFP testing, triple or quad screening) for certain birth defects. It is important that you understand this screening process so that you can decide whether or not to be tested.

What is the purpose of this screening?
Maternal Serum screening is done to determine if a pregnant woman has an increased risk of having a baby with certain birth defects.  The blood test measures four proteins in your blood which can help identify if you have a higher chance of having a baby with a neural tube defect (spina bifida), Down syndrome, or Trisomy 18.  Babies with these birth defects may have certain features that can be seen on ultrasound, but in general, they cannot be diagnosed by ultrasound alone.

What is a neural tube defect?
A neural tube defect occurs very early in pregnancy when the cells that become the skull, brain, and spinal column fail to form a closed tube. If there is an opening along the lower portion of the tube, the spine does not close completely. This is called spina bifida. Complications may include problems with walking and bowel and bladder control. If this tube does not form correctly at the top, the brain and skull will not develop. This is called anencephaly. Babies with anencephaly do not survive.

What is Down Syndrome?
In each of our cells, we have 46 chromosomes, or 23 pairs. They give instructions for our development. Down syndrome results when there is an extra chromosome on “pair 21”. The baby has three of chromosome 21 instead of two. Any woman can have a baby with Down syndrome, although the risk increases with the age of the mother. Babies with Down syndrome have some degree of mental retardation, as well as other physical problems.

What is Trisomy 18?
Trisomy 18 results when there is an extra chromosome on “pair 18”. The baby has three of chromosome 18 instead of two. Babies with trisomy 18 have severe birth defects, severe mental retardation and rarely live long after they are born. Most do not live past one year.

What does it mean if my screen is negative?
A negative test result means that the likelihood of your baby having a neural tube defect, Down syndrome, or trisomy 18 is reduced. However, a negative screen does not guarantee that the baby will be normal, because maternal serum screening does not identify all unborn babies with these problems. Nor will it diagnose other birth defects a baby may have.

What does it mean if my screen is positive?
If your screen is positive, it means that your unborn baby is at increased risk for a problem. It does not mean that your baby has a birth defect. The vast majority of women with “screen positive” results do not have babies with Down syndrome, trisomy 18, or a neural tube defect. However, if your screen is positive, you may want to consider other tests such as: ultrasound, repeat blood tests, or amniocentesis. Follow up options are determined privately between a woman and her doctor.

Whether or not you have more testing is up to you. Remember the maternal serum screening test is not a diagnostic test. It will not tell you whether or not your unborn baby has or doesn’t have a problem. It will simply indicate the chance that the baby has a problem.

Who might decide NOT to have a screening?
Knowing about these problems ahead of time may change the management of your pregnancy and your delivery. However, some women decide that they do not want to know during the pregnancy if their baby has one of these problems. If this is your decision, you should not have your blood drawn.

If you have any questions or concerns about having this test done, we encourage you to talk with your doctor.