This article traces the development of prenatal screening programs for Down syndrome from maternal age to second and then first trimester screening. Future possibilities for noninvasive diagnosis are also presented.
- The prenatal diagnosis of Down syndrome currently requires an invasive test (either amniocentesis or chorionic villous sampling) with an inherent risk of miscarriage.
- If invasive testing were conducted in all women of advanced maternal age, only up to 30% of cases would be detected. Further, only about one in 140 would carry an affected fetus.
- Second trimester screening for risk of Down syndrome (serum and/or ultrasound-based) can be undertaken in pregnant women of any age.
- First trimester screening for risk of Down syndrome (ultrasound and/or serum-based) is now available in some centres.
- A noninvasive diagnostic test for Down syndrome using fetal cells or fetal DNA isolated from maternal blood may become available in the next decade.