Three prenatal tests can determine if Fragile X is present in the fetus. CVS is not widely used and carries a 1-2 percent risk of miscarriage following the procedure. Amniocentesis is the removal and analysis of a small sample of fetal cells from the amniotic fluid.
Amniocentesis is widely available and involves a lower risk of miscarriage.
However, amniocentesis cannot be done until the 15th to 18th week of pregnancy and it usually takes an additional 2 to 4 weeks for the cells to grow and be analyzed. So a woman may have to wait until the 17th to 22nd week of her pregnancy to have the results of this test. However, PUBS is not widely available, PUBS is not done until the 18th to 22nd week and carries the greatest risk of miscarriage.