Q: What is a nuchal translucency screening? Should I have one?

A: A nuchal translucency screening (also called an NT or nuchal fold) is a special ultrasound that's usually done between 11 and 14 weeks into your pregnancy, along with blood tests, to look for signs that a baby may have genetic problems like Down syndrome or Trisomy 18.

Babies with these conditions may have slightly thicker necks than other babies, so the ultrasound examines this area to determine a baby's risk. This test can't give you a definite diagnosis, but it can help you decide whether to get further testing. If the test discovers that the back of the neck is thicker than average and the blood tests also pick up signs of the conditions, the couple is usually referred for genetic counseling and possibly chorionic villus sampling (CVS) or amniocentesis to confirm the diagnosis. Sometimes, the ultrasound may show that baby's neck is thicker than average, but the blood test results may rule out Down syndrome. If this is the case, your baby may have a slight heart defect and your doctor will likely run further tests to know for sure.

Currently, the American College of Obstetricians and Gynecologists (ACOG) recommends that all moms-to-be be offered a nuchal translucency screening, but whether you decide to have one is up to you and your doctor. (The test is also still pretty new, so it may not be available in all areas.)

• Because the screening is completely noninvasive, some women choose to get it automatically, figuring that the results will either reassure them that their babies are developing on track or give them more time to consider their options if a problem is detected.

• Other women -- especially those whose babies face a higher risk of developing these conditions -- may choose to skip this screening and get a more accurate (and invasive) test like CVS right away. (The risk of having a baby with Down syndrome and Trisomy 18 increases with age and family history, for example.)

• And others -- like those whose babies face a low risk of these conditions -- may choose to skip the test altogether. If you have questions, your doctor should help you decide what's right for you.

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