Irene Park was 37 years old, six weeks pregnant and worried. She was cramping and bleeding. When her blood tests showed low levels of HCG, a hormone vital to maintaining early pregnancy, her doctor confirmed what she feared most: She was going to have a miscarriage.
Park was devastated. She had endured in vitro fertilization (IVF) to become pregnant, and to learn that she was having a miscarriage seemed too much to bear. But two weeks later, when she returned to the hospital, doctors discovered she was still pregnant with a viable embryo. Park was rattled but extremely relieved.
At the next visit, her doctor recommended genetic testing. Park, who wanted no more surprises, readily agreed. Thirteen weeks into her pregnancy, she had her blood drawn, and 10 days later she received good news: Not only was her fetus viable, it was also most likely free of the more common chromosomal disorders.
“I was so worried my whole first trimester,” Park says. “After taking the test I felt such peace of mind. I was also happy to find out I was having a girl.”
Help for parents-to-be
Park’s is a textbook case of how prenatal genetic testing can help parents-to-be. Because she was older than 35, she was at higher risk for carrying a fetus with genetic disorders. Because she had complications, she was eager for any additional information that could ease her worries about the pregnancy.
For many parents, genetic testing can offer peace of mind. Just a few decades ago, the only way to detect genetic disorders was to have the pregnant woman undergo an amniocentesis, an invasive procedure that can put both the fetus and the mother at risk.
Today, there is a variety of screening tests that measure risk for genetic disorders through simple blood draws (see chart below). In Park’s case, she took the newest and most accurate blood test available: a cell-free DNA (cfDNA) or non-invasive prenatal test (NIPT). CfDNA tests have a significantly higher rate of accuracy than other blood tests that screen for genetic disorders. This means that women like Park who receive normal test results can skip invasive diagnostic tests like amniocentesis or chorionic villus sampling (CVS), and they can rest assured that their baby will most likely be born without the most common chromosomal disorders.
Though these tests can give reassurance, a normal screening result does not definitively mean that a baby will be born without genetic disorders. Corporate-sponsored studies have shown that the cfDNA test has up to 99 percent accuracy in predicting increased risk for Down syndrome and 98 percent for Edwards syndrome (trisomy 18), but only 65 percent for Patau syndrome.
Because of this uncertainty and disputes over rates of false positives, women whose cfDNA results show increased risk for a genetic disorder need a follow-up amniocentesis or CVS to obtain a definitive answer. These diagnostic tests can confirm or negate the results of an abnormal screen as well as test for a host of additional genetic disorders. Although there are no cures for these conditions, early detection can be useful for two reasons: Parents can start preparing to raise a child with disabilities, or they can opt for early termination of pregnancy. Especially in the cases of Edwards and Patau syndromes, which are often fatal, an early termination can spare the complications of a later procedure, or the pain of giving birth to a stillborn baby or a baby likely not to survive beyond its first month of life.
More tests, more problems?
While prenatal genetic testing can offer relief for some parents-to-be, for others, it can bring more worries. I, for one, spent most of my recent pregnancy anxious about test results that showed a high risk for Down syndrome. If Park’s was a textbook case of how genetic testing can help, mine was a textbook case of how genetic testing can harm.
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