Testing for Fetal Impairments

By OBOS Pregnancy & Birth Contributors | April 7, 2014

Ever since the 1970s, it has been possible to get some information during pregnancy about the characteristics of the developing baby. In recent years, the number of tests available to pregnant women has multiplied, allowing increased scrutiny of the fetus for specific disorders.

Women may choose prenatal testing to learn about health problems, diseases, or disabilities that might occur. If you learn through prenatal testing that your baby will likely be born with a correctable, treatable, or lifelong impairment, you may want to make special plans before the child’s birth. Or you may decide to end the pregnancy if you know that your future child would have a disabling condition or be unlikely to survive after birth.

Though prenatal tests may offer useful information, they also raise concerns if the report is false-positive. Most of the noninvasive tests (blood tests and ultrasounds) are screening exams that are not perfect, and they can indicate a problem that with further testing will turn out not to be there. Invasive tests such as amniocentesis or chorionic villus sampling (CVS) can give you a 100 percent true answer about some genetic conditions, but these tests, which involve drawing fluid out of the amniotic sac by inserting a needle through the abdomen or vagina, carry a very small risk of miscarriage. Even when they do not cause medical problems, tests can create anxiety and expense and add to the medicalization of pregnancy and birth.

I had a CVS [chorionic villus sampling] done, which was both physically and emotionally painful. We found out there were some irregularities, so I ended up needing an amnio as well. It turned out the irregularity was some fluke in the test, and we finally got a clean bill of health [for the fetus]—six months into the pregnancy. The waiting was excruciating. To be pregnant but not be able to let yourself feel the joy and hope of it was truly horrible.

Tests for fetal impairments give us both the opportunity and the responsibility to decide whether we want to become parents of a child with a particular set of characteristics. Some of us may decide that we don’t want this information. Others of us are eager to know all we can about our developing baby. Your doctor or midwife may strongly recommend testing, but it should not be automatic; decisions about testing are up to you.

Types of Tests

Three types of tests screen for or diagnose disorders in the fetus:

  • Genetic carrier testing is blood tests that can be performed before you get pregnant or in early pregnancy. The tests determine if you or your partner is a carrier of diseases that can be inherited by your children. Examples of genetic carrier tests are blood tests for sickle-cell anemia or cystic fibrosis.
  • Screening tests measure the likelihood that your fetus has a particular condition but can not tell for certain whether the fetus has the condition. Examples of screening tests are ultrasounds and “maternal marker” blood tests. Screening tests are typically used to determine if a diagnostic test is necessary.
  • Diagnostic tests give a yes-or-no answer, identifying whether the fetus does or does not have a particular condition. Examples of diagnostic tests are amniocentesis and chorionic villus sampling.

It is important to note that none of the tests guarantees that the baby will be healthy; instead, they are designed to ask, and answer, one specific question, such as: “Does my baby have cystic fibrosis?”

For more information about specific tests for fetal anomalies, visit the Prenatal Testing pages on the March of Dimes website.

Questions to Consider About Testing

Before choosing whether or not to have any test, find out what information the test is capable of providing and its advantages and disadvantages. Ask your health care provider, and do your own research, to find out the following:

  • Does the test pose any risk to you and/or your developing baby?
  • Why is this test recommended for you? Are you in a group that makes you or your baby more likely to have this condition?
  • When can you expect the results to come back?
  • How reliable is this test? What is the incidence of false-positive results? If you get a result described as abnormal or unusual, what kind of follow-up testing or counseling will be offered?
  • What are your options after receiving the result? Are there any treatments available for you or for the fetus if the result is abnormal?
  • How much will this test cost? Will your health care insurance cover part or all of the cost of this test? If not, can you get any financial assistance?
  • Would knowing that my baby will have a particular condition make a difference in my decision to continue my pregnancy? If so, how?
  • What do I know about life with these conditions?
  • Would knowing any other characteristics detectable by prenatal testing, such as the sex of my baby or the identity of the father, affect my decision about continuing my pregnancy? If so, how?