With the help of ultrasound, a piece of placenta can actually be sampled. This is done by inserting a catheter through the vagina and into the uterus. In some cases, due to the location of the placenta, a needle is inserted into the uterus through the abdominal wall. CVS can detect the same chromosomal defects as amniocentesis, but it cannot diagnose open neural tube defects. Depending on the type of analysis you need, results may be available within twenty-four hours or can take up to two weeks.
Some doctors report that results can take as long as four weeks.
However, you will need to have a serum AFP done again at fifteen to sixteen weeks if you go the CVS route. There are risks. First, CVS carries a slightly higher risk of miscarriage than amniocentesis. Studies suggest that if the test is performed before ten weeks, there can be an increased risk of fetal limb development problems. Occasionally, chromosome variants, or mixtures of cell types, make interpretation difficult.