Noninvasive screening tests performed during your first trimester can give you valuable, if inconclusive, information about your baby’s risk for Down syndrome and other chromosomal abnormalities. Diagnostic DNA tests can be performed as early as the first trimester and can conclusively tell you what blood tests and ultrasounds cannot. Certain prenatal tests can also determine the father of your child, if paternity is in question.
Why Performed
At the time your baby is conceived, you and your child’s father each pass down 23 chromosomes to your baby, for a total of 46 — an equal mix, according to the Cleveland Clinic. Fetal cells bear DNA markers of a baby’s biological mother and father and, when collected even in small amounts, can yield information about birth defects associated with your child’s genetic makeup. Prenatal testing is typically conducted to determine the presence of chromosomal or genetic conditions or neural tube defects within a strong degree of certainty. Early DNA tests on pregnant women are typically not performed to establish paternity, although they can also serve this function.
Paternity Testing
Prior to scientific advances made in DNA testing, establishing the paternity of a child born out of wedlock was tedious and sometimes impossible, relying on vague or subjective evidence, such as a child’s physical resemblance to the putative father — the man a woman names as her child’s father without proof — as well as the nature and history of the relationship. Early methods used blood testing, which either excluded or included a man from the possible paternity pool. Modern-day DNA testing can establish paternity within 99 percent degree of certainty — however, these tests are typically done after the child is born by taking cheek swabs of mother, child and putative father. Due to the risk of miscarriage, early DNA testing — tests performed before a baby is born — is generally discouraged.
Chorionic Villus Sampling
Chorionic villus sampling (CVS) is the earliest type of DNA testing that can be performed on a pregnant woman. This test, which is conducted between the 10th and 12th week of pregnancy, involves taking a sample of the placenta through a needle or tube that is inserted through the cervix into the uterus. The risk of miscarriage as a result of this test is 1 in 100, according to MayoClinic.com.
Amniocentesis
Amniocentesis is another prenatal diagnostic test that’s performed slightly later than CVS — after the 15th week of pregnancy. This test is done by obtaining a small sample of amniotic fluid through a needle that’s inserted through the abdomen. The risk of miscarriage is also slightly less: 1 in 300 to 500.
Other Information
The cost of DNA testing can vary greatly; however, the American Pregnancy Association indicates that, as of 2010, you’ll pay $400 for a noninvasive buccal swab test or up to $2,000 for most costly tests, such as CVS and amniocentesis. Prenatal DNA testing can be done to determine the identify of a child’s biological father, but this must be weighed against the risk to the developing fetus, says the Cleveland Clinic. Of additional concern is how you intend to use the results of the tests — to be considered evidence, DNA testing must be conducted by unbiased parties, with results subject to chain of evidence procedures to ensure their integrity in court. Seek legal counsel if you intend to use the results of prenatal DNA testing for purposes of establishing paternity.
