After cleaning the skin, a very fine needle is inserted into the uterus watching the needle all the time on the ultrasound screen. The needle is removed and the fetus is again checked. After waiting for about 20 minutes you are then able to return home. Patients usually feel far less discomfort from the test than they expected - many indicate that it is not even as bad as a simple blood test. If you are worried about the test nitrous oxide, the gas used in labour, is available, although most patients find they do not need it.
Amniotic fluid contains cells which have been shed by the fetus.
They are allowed to grow in the laboratory until there are enough to test the chromosomes. Each of the chromosomes from a number of cells is carefully examined to check that the correct number of cells is carefully examined to check that the correct number are present ad that the appearance and length of each chromosome is normal. The sex can also be determined by looking at the chromosomes - you can find this out if you ask your doctor. The laboratory will usually have the chromosome result available in 2 weeks - your doctor will be informed and he or she will pass it onto you. The results of the test for spina bifida will be available at the same time.