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Various tests are available to measure, under very carefully controlled conditions, the length of time it takes to produce certain components of the final fibrin clot. Tests called assays can also determine the percentage of factors VIII and IX present compared to normal percentages. This information can help in demonstrating the type of hemophilia present, as well as the severity.
Individuals with a family history of hemophilia may benefit from genetic counseling before deciding to have a baby. Families with a positive history of hemophilia can also have tests done during a pregnancy to determine whether the fetus is a hemophiliac. The test called chorionic villous sampling examines proteins for the defects that lead to hemophilia. This test, which is associated with a 1% risk of miscarriage, can be performed at 10–14 weeks. The test called amniocentesis examines the DNA of fetal cells shed into the amniotic fluid for genetic mutations. Amniocentesis, which is associated with a one in 200 risk of miscarriage, is performed at 15–18 weeks gestation.
— Jennifer F. Wilson, MS
