Amniocentesis is a simple medical procedure used to obtain small samples of the amniotic fluid surrounding the fetus.

In the first half of the pregnancy (between the 14th and 18th week) the doctor may perform an amniocentesis when:

• The age of the mother is 35 years of age or older. The risk of bearing children with chromosomal birth defects increases as a woman ages, thus if a woman will be 35 or older at the time of delivery, most physicians offer the option of prenatal testing for chromosomal...