Chorionic Villus Sampling (CVS)
This test is usually done at 10–12 weeks after the first day of the mother’s last menstrual period. Thus it is important to see your doctor as soon as you realize you are pregnant.
The test is done by looking at cells taken from the developing placenta, called the chorionic villi. A thin catheter, or flexible tube, is inserted through the vagina and cervix, and small amounts of the chorionic villi are sampled. Alternatively, the test is occasionally done by inserting a needle through the mother’s abdomen to obtain chorionic villi. In either case, the cells are tested in the laboratory for the presence of the HD mutation. No anaesthetic is required for this procedure. When the test is carried out by an obstetrician experienced in the technique, the risk of miscarriage related to the test is about 1% (1 in 100 pregnancies).