Your Guide to Prenatal Tests
The what, when, and why of 30 pregnancy exams, screens, and scans
Who: Women over 35, those who have—or whose partners have—a family history of genetic diseases, and those whose triple screen test results are abnormal
When: At 15 to 20 weeks
How: Guided by ultrasound, a doctor inserts a needle into the abdomen to draw a sample of amniotic fluid. Most women report it’s not as uncomfortable as it sounds.
Why: An amnio detects neural tube defects, Down syndrome, and other genetic disorders such as cystic fibrosis and thalassemia.
Results and follow-up: The test is 99 percent accurate; results are available in seven to ten days. A faster test, known as "FISH" (fluorescent in situ hybridization), can return results sooner, in two or three days. The miscarriage rate for the procedure is about one in 400.