The chances of a parent of a child with Trisomy 21 having another child with Down Syndrome is approximately 1 in 100. Parents of children with translocation type of Down Syndrome should have chromosome analysis to detect a carrier state. The pregnancy miscarried about half-way through. Until recently, the answer was to offer amniocentesis to all pregnant women age 35 or older and to those women who had a previous child with Down Syndrome. Now some doctors reccommend screening tests for all pregnancies.
Tests are of two types- diagnostic and screening.
Diagnostic tests sample fetal cells and give a definitive diagnosis. Screening tests are relatively simple tests that find most of the fetuses with Down syndrome, but they also find some without. Screening tests need to be confirmed by a diagnostic test. These cells are then sent for chromosome analysis. Ultrasound is used to safely pass the needle.