Birth Defects Testing

Is a Birth Defect Test Accurate?

No test is 100% accurate. A screening test may be negative even when the baby has a birth defect. This is called a false-negative test result. It also is possible that a test will be positive—meaning the test result is abnormal—but the baby does not have the problem. This is called a false-positive test result.

A screening test will tell you about your chance of having a baby with a birth defect. If the screening test shows an increased chance, your doctor will probably want you to have chorionic villus sampling or amniocentesis to find out for sure if the baby has a problem.

The first-trimester screening (FTS) correctly finds Down syndrome up to 85% of the time. And the integrated screening correctly finds Down syndrome about 95% of the time.¹

Almost 100% of neural tube defects, such as anencephaly, are found by ultrasound.³

Chorionic villus sampling or amniocentesis have an accuracy rate of more than 99% for Down syndrome.⁴

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Author:	Sandy Jocoy, RN	Last Updated: May 20, 2008
Medical Review:	Sarah Marshall, MD - Family Medicine Siobhan M. Dolan, MD, MPH - Reproductive Genetics
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