There’s a lot of misunderstanding about the tests that are available to a pregnant mother to look at the health of the fetus. I know there are misunderstandings because I hear them everyday from patients. This is a list of the most common ones.
The Maternal Serum Screen proves that my baby has normal genetics.
This is not a test of the baby, it is a measurement of chemicals in the mother’s blood.
The relative amounts of the chemicals are measured in the lab. Over many years, we have come to understand that pregnant women with some mixtures of these chemicals are more likely to have a baby with Down syndrome, Trisomy 18, or spina bifida. That’s why some people call the ‘Down syndrome test’.
Answer: No. This is not a test of the baby and it gives no information about the baby’s genetics. It is just the first step in helping you decide about other testing.
If the Serum Screen is normal, then my baby can’t have Down syndrome
There is no such thing as “normal” for this test. It isn’t a measure of normal and abnormal. It is showing where you are in a range of possibilities. Just like measuring your height doesn’t tell normal or abnormal, just where you are in a range. The results of the serum screen are combined with information from the ultrasound(s) and the mother’s health history to give a risk assessment: the chance that the fetus has one of the listed problems. If the chance is high, then you may wish to do more testing. If the chance is low, you may be satisfied with the answer. But, a chance of 1 in 5,000 is still a chance: no risk is zero.
Answer: No, the test just tells you where you are in a range. You still have some risk that the baby will have Down syndrome.
The Serum Screen said that my baby would have Down syndrome, but she doesn’t. Why did the doctor lie to me? Why was the test wrong?
The doctor didn’t lie to you and the test wasn’t wrong. Remember, this isn’t really a test that measures normal versus abnormal: it is just telling you where you are in a range. Some normal people fall out of the range and are told they are abnormal when they really aren’t. This is what happened to you. Also, the test didn’t say that you were ‘going to have a baby with Down syndrome’. It told that your risk was higher than expected for your age and general health. You were probably offered other testing when the result came back that would give more of a ‘normal versus abnormal’ result. It was then up to you to decide whether you wanted more testing.
Answer: The test told you that your risk was higher than expected, not that your baby had Down syndrome. This was a chance for you to make a decision about other testing.
Ultrasounds will find everything important
Ultrasounds are great tests for looking at the structure of the fetus’ body. But not all ultrasounds look at everything in great detail. Lots of other things will interfere with what an ultrasound sees. The fetus may be positioned in such a way that some body parts are hard to see. The placenta might be in the way. There may be more than one fetus and it might be hard to tell them apart. A fetus who is moving around a lot can be difficult to examine with ultrasound. Low amounts of fluid around the fetus make ultrasounds not work as well. It is much harder to see the fetus is mother is overweight or obese.
The amniocentesis test isn’t about how you manage your pregnancy. It is a way of getting information that helps you make decisions. What you do with the information from the testing is a separate thing. A normal test result may be very reassuring to you. If the ultrasounds are abnormal and the amniocentesis sample testing is normal, that can be frustrating. An abnormal test result will let you plan for the birth of an affected child or, yes, can lead you to decide to terminate the pregnancy.
If you discover at 18 weeks of pregnancy that the fetus is affected with a serious genetic condition, it gives you the chance to choose a hospital that can care for the baby after delivery. It is information that will let you make extra arrangements at home, with your work, and with your family. It also lets you deal with the emotions you have so that the day the baby is born is a celebration of the baby – not the day that you find out something is wrong.
Also, we sometimes don’t make the decisions that we think we will make once we learn new information.
Angela Scheuerle M.D., F.A.A.P , F.A.C.M.G is pleased in providing relevant information about genetics. Consider her practice if you are seeking a genetic consultation in Dallas.
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