A healthy baby is every expectant mom’s No. 1 priority. The good news? Most babies are born healthy. But a small amount (about 2 percent to 4 percent) are affected by some kind of a serious birth defect. There are a number of tests that can check on your baby’s health when you’re pregnant: Screening tests give parents-to-be an idea of the likelihood that their baby has certain kinds of problems, one such test has been in the news lately.
A recent study published in The New England Journal of Medicine found a fetal DNA test to be 10 times more accurate in testing for Down syndrome than the currently-used blood test and ultrasound. It was also five times more accurate in testing for trisomy 18, another genetic disorder. Ultimately, researchers hope this could reduce the need for invasive follow ups to positive blood tests. (The test is expensive, so talk to your doctor about whether or not DNA sequencing is right for you.)
Typically, though, when a screening test shows a potential problem, your provider will suggest diagnostic testing to learn more. Diagnostic tests are performed on genetic material from the baby to determine whether he or she has a birth defect. Here, the most common prenatal tests, and what the results could mean.
Weeks 10 – 13:
Chorionic Villus Sampling (CVS)
What does it test for? Chromosomal abnormalities, such as trisomy 21, trisomy 18, trisomy 13, and single gene disorders, such as cystic fibrosis.
How is it given? A provider takes a small sample of cells from the placenta, which has the same genetic material as the baby, in one of two ways: During a trans-abdominal CVS, a provider inserts a thin needle through the mother’s belly and into the uterus to take a small sample of placental tissue; or, with a transcervical CVS, a provider inserts a thin tube through the mother’s vagina and cervix to take a tiny sample of placental tissue. The sample is sent to a laboratory, where the chromosomes in the cells are checked to see if they are missing or damaged. CVS results come back in about one or two weeks. After the test, women may experience cramping and they may have some spotting. (Women who have this test should call their provider if they have heavy bleeding or a fever, or if they start to feel contractions.)
Is there a risk? Yes, but it’s low: CVS carries a less than 1 in 300 to 500 risk of miscarriage.