Couples often ask when a miscarriage would occur. This is a difficult question because at least two out of three miscarriages after amniocentesis are totally unrelated to the test itself and would have occurred anyway. However, if you have had no problem by three weeks then any complications is very much related to the experience and expertise of the operator. The test, like any other, may fail because no specimen is obtained or because the laboratory are unable to grow cells. Both of these are very uncommon.
Incorrect results are extremely rare.
Occasionally uncertain results may occur - these may need a further test such as a sample of fetal blood to sort them out. If you lose blood or clear fluid from the vagina after the test then you should contact your own doctor. Those few patients in whom the tests show that the fetus has an abnormality will be given information so that they can make a choice about whether to continue the pregnancy. It is still possible to perform a termination of the pregnancy at this stage. Counselling is available to help couples make their decision.