By mapping out specific chromosome pairs, a scientist can readily identify the sex of a particular fetus. In humans, chromosomal defects can result in a variety of disorders, including mental retardation and diseases. By identifying any future problems, the parents will have to consider either aborting the pregnancy, or letting it continue and facing the problems they might encounter and have to deal with. There are many reasons for amniocentesis. Certain women 35 years old or older have a greater than average chance of giving birth to an infant with a chromosome problem.
Women are also at risk if they have already had a child with a genetic disorder.
Continuous ultrasound monitoring is used during insertion of the amniocentesis needle. Care is taken to avoid placing the needle near the baby. This is not significant. This is very rare. A slender needle is inserted into the woman's abdomen and into the uterus.