A New, Less Invasive Option for Testing for Birth Defects

For many years amniocentesis has been the primary method of testing pregnant women for potential genetic diseases in their fetuses. Amniocentesis is a procedure that involves inserting a needle into a pregnant woman’s uterus. A sample of amniotic fluid, which contains fetal tissues, is used to determine if the fetus has any chromosomal abnormalities.

Amniocentesis is typically performed around week 16 of pregnancy. The procedure is typically only used with pregnant women who are at high risk for birth defects, such as age (35 and older) or a negative indicator showing up on an ultrasound, because it is highly invasive and causes miscarriage in about 1 in 300 to 1 in 500 pregnant women.

In 2011, a new, less invasive test became available called Cell-Free DNA Testing. The test can determine if a woman is at increased risk for having a child with Down syndrome, Edwards syndrome, or Patau syndrome. The test is performed at about week 10 of pregnancy (6 weeks earlier than amnio) by taking a sample of the woman’s blood. The test measures the relative amount of free fetal DNA in the mother’s blood to determine the relative amount of DNA from the specific chromosomes that cause the genetic disorders. The test can also determine fetal sex.

The test is about 99% accurate in indicating chromosomal abnormalities, and it only determines risk of birth defect. It is not as comprehensive as amniocentesis to this point, but it is 10 times better than standard blood testing and ultrasound. It does not carry the risks of amniocentesis and is quickly becoming the more popular option. Amnio testing has dropped by about 50% in recent years.

Free fetal cells were first discovered in the mother’s blood stream by a Hong Kong chemist in 1997. Since that time research into cell-free DNA has expanded. The test continues to be improved and now offers a method for testing for microdeletions, or DNA imperfections, that can lead to heart deformities and immune problems in babies.

The test is, like amniocentesis, typically only used in women who are at high risk for having babies with genetic disorders, but in some places, it is available to all pregnant women. This raises questions of ethics because parents can learn much more about the genetic makeup of their future child, which brings up issues of designer babies and abortion.

Cell-free DNA testing can cost as much as $2,800 and may not be covered by insurance as it is still considered by many insurance companies to be experimental and explorative. However, many facilities will help parents offset the cost.