If you’re pregnant, you’re no stranger to prenatal testing. Routine prenatal care requires multiple tests to screen for potential maternal and fetal health problems. What these tests are, and when they are given, however, are beginning to change.
Two common prenatal tests are the quad screen or “triple screen,” offered to women between weeks 15 and 20 of pregnancy, well into the second trimester. These tests measure certain proteins and hormones in the maternal blood to determine whether the fetus is at risk for certain abnormalities, including Down syndrome or neural tube defects. An abnormal test result does not diagnose a problem, but simply indicates that further testing is warranted.
First trimester screening for Down syndrome
While testing in the second trimester offers the opportunity to prepare for a child who may have special health needs and developmental issues, many parents wish they could be made aware of potential health issues during the first trimester of pregnancy. A new test, called nuchal translucency, provides just that option.
The risk of having a baby with Down syndrome increases with maternal age, but the possibility exists in all pregnancies. The only way to know for sure if a fetus has a chromosomal abnormality is for the mother to undergo invasive testing like chorionic villus sampling (CVS) or amniocentesis. These tests, however, carry a small risk of miscarriage, so researchers have developed noninvasive screening tests to determine which pregnancies are truly at the highest risk.
First-trimester screening using a combination of nuchal translucency and maternal serum testing offers several potential advantages over second-trimester screening. Negative results can reduce the expectant mother’s anxiety level weeks earlier, while positive results can ensure a woman has time to discuss diagnostic options with her doctor. If she chooses to undergo diagnostic testing, she could opt for CVS right away, instead of waiting for amniocentesis later on in pregnancy.
Nuchal translucency has been in limited use since the mid-1990s, and is recommended only if performed at certified centers where appropriate ultrasound training and ongoing quality-monitoring programs are in place. While training and ongoing quality assurance improve detection rates dramatically, nationally standardized quality control systems to ensure the reliability of the test, and the accurate assessment of risk, are still to be finalized. Nevertheless, the test is increasingly available at major medical centers.
The comfort of knowing
First trimester tests such as nuchal translucency and maternal serum testing can provide early, reliable information—information that will either provide peace of mind or will enable parents to formulate a definitive plan of action with their doctor and genetic counselor.
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