Birth Defects Testing Gives Parents Choices

A mother can do a lot to reduce her risk of giving birth to a baby with birth defects. She can eat a healthy diet, avoid alcohol and cigarette smoke, and take extra precautions with her medications. Still, sometimes babies are born with birth defects and no one can explain why. Birth defects testing performed during pregnancy can detect possible problems with the fetus, which can help prepare parents for various potential outcomes.

Types of Birth Defects Testing

There are two main types of tests that can help detect certain birth defects:

1. Screening tests: These include blood tests and ultrasounds, which can show the chance that a baby has a certain birth defect, but can’t tell you for sure. A positive result from a screening test shows that the baby is more likely to have that birth defect than other babies who test negative. If you receive a positive result, your doctor will probably recommend you have a diagnostic test to provide more information.
2. Diagnostic tests: These tests can more accurately show if a baby has a certain birth defect, though they are more invasive and carry higher risks, as they typically involve removing some of the baby’s cells to examine genes and chromosomes.

Neither of these types of tests are 100 percent accurate, but they can give parents more information about the development of their child.

Specific Birth Defects Testing

Specific birth defects tests within the former two categories include the following:

1. First trimester screening: This type of prenatal testing is performed between 11 and 14 weeks of pregnancy to detect Down syndrome and trisomy 18. Blood tests measure the level of pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG) in the mother’s blood. As a second part of the screening, an ultrasound exam measures the thickness at the back of the neck. The results of these two tests plus the mother’s age are used together to assess the risk to the fetus.
2. Second trimester screening: This type of prenatal testing is performed around 15-20 weeks of pregnancy to screen for Down syndrome, trisomy 18, and neural tube birth defects. Again, blood tests are performed to measure the level of three or four of the following: alpha-fetoprotein (AFP), estriol, human chorionic gonadotropin, and inhibin A. When all four substances are tested for, this screening detects Down syndrome in 81 percent of cases, and neural tube birth defects in 80 percent of cases. In addition, abnormal levels of AFP can signify spinal cord defects and abdominal wall defects.
3. Combined results: The results from both of these screenings can be used together to increase the chances of detecting Down syndrome.
4. Chorionic villus sampling (CVS): This is a diagnostic test where doctors look at the cells from the placenta. It’s usually done between 10-12 weeks of pregnancy. The doctor threads a thin flexible tube (catheter) into the uterus through the vagina. This test may detect Down syndrome, sickle cell disease or cystic fibrosis.
5. Amniocentesis: Performed between 15-20 weeks of pregnancy, this diagnostic test again looks at the baby’s cells, but this time from the amniotic fluid that surrounds the fetus. The doctor puts a needle through the belly and into the uterus to collect the fluid. This test can find neural tube birth defects like spina bifida.
6. Cordocentesis (also known as Percutaneous Umbilical Cord Blood Sampling or PUBS): This diagnostic test examines blood from the fetus to detect abnormalities. A needle is inserted into the umbilical cord to retrieve a small sample of blood. The test is performed after 17 weeks, and detects Down syndrome, blood disorders, infections, fetal anemia, and certain malformations.
7. Ultrasound: This test may be performed between 18 to 20 weeks, and uses high-frequency sound waves to form images of the fetus. This test can detect features related to some birth defects, like a thick neck for Down syndrome, or problems of the heart, spine, belly, or other areas.

Genetic Testing Also Available

There are also certain types of genetic testing parents can go through prior to pregnancy, to see if they carry certain defective genes. Cystic fibrosis screening is a blood test that determines if one carries the defective gene that causes the disease. A positive result shows that partners may have an increased chance of having a baby with cystic fibrosis.

Genetic testing during pregnancy can also help diagnose genetic abnormalities before birth. Parents with a family history of genetic disorders may choose to undergo these tests. They are performed using the same techniques as those mentioned above, and can diagnose genetic disorders like Down syndrome, Duchenne muscular dystrophy, hemophilia A, sickle cell anemia, polycystic kidney disease, and Tay-Sachs disease.

Who Should Request Birth Defects Testing?

Parents may want birth defects testing because there is a family history of certain diseases or disorders, or because they are worried about certain types of birth defects. Some parents want the option of deciding whether or not to continue the pregnancy should a birth defect be detected. Not all moms should go through birth defects testing, however, including those who are worried about the risk of miscarriage—both CVS and amniocentesis carry a very small risk. Some parents may have insurance that does not cover the tests, in which case they may be too expensive.

Regardless of which types of birth defects testing you may elect to have, talk to your doctor about the risks involved, as some tests may prove incorrect or give false positive or false negative results. Taking charge of your health and lifestyle habits can go a long way toward preventing birth defects, while additional tests can help if you’re particularly concerned and want to have additional information about your pregnancy.