The preliminary findings should be available within three working days. This will notify you whether a chromosomal disorder, such as Down syndrome, Edwards syndrome, or Patau's syndrome, has been discovered. If uncommon disorders are also tested for, it may take 2 to 3 weeks or longer for the findings to be returned. This is a very important test because it allows doctors to find out early on if your baby has any birth defects. Also, with Down syndrome pre-natal diagnosis can help parents decide what future actions to take (such as having more children or undergoing amniocentesis/karyotyping). Chorionic villus sampling is a procedure used to obtain samples of the developing fetus for examination. It is performed at about six weeks' gestation, just after the fetal blood vessels have developed enough to allow for easy access. The sample is taken from the chorion, the thin outer layer of the uterus that contains many blood vessels and connects the fetus to its mother. This test is usually done on an outpatient basis. You may be asked to wait in a room until the procedure is over. Local anesthesia is given to the area where the needle will be inserted into the uterus. Then, a small piece of tissue containing several blood vessels and connected to the fetus is removed through a hollow needle. There are no serious side effects associated with this procedure.