Amniocentesis
This is a procedure used to evaluate the health of your unborn baby and identify any problems that may exist. Using ultrasound as a guide, a thin needle is inserted through your stomach into your uterus (womb). A small sample of the amniotic fluid that surrounds your baby is then taken. This fluid contains cells from the baby, which are then studied in the laboratory.
The best time to perform amniocentesis is in the 16th week of pregnancy.