What is first trimester screening (FTS)?
This test is designed to identify pregnancies at an increased risk for Down syndrome and trisomy 18 early in the pregnancy. It does not diagnose either condition but provides an adjustment of a woman’s age-related risk. For example, a 35 year old woman has a risk of approximately 1/270 for Down syndrome. FTS will provide an approximate risk value either equal to, higher (e.g., 1/15) or lower (e.g., 1/1000) than 1/270. Many women use FTS risk adjustment prior to determining if they want a diagnostic procedure (i.e. amniocentesis or chorionic villi sampling), as these diagnostic tests have ~0.5-1 % risk of pregnancy loss.
