Amniocentesis - How and Why it is Done

An amniocentesis is the procedure in which a physician, usually an ob/gyn, removes some of the amniotic fluid from the amniotic sac during pregnancy. The fetus is in the uterus surrounded by the amniotic fluid. This procedure is routinely done between fifteen and eighteen weeks pregnant. There is enough fluid at this point in pregnancy and if there is a serious problem, the parents still have time to terminate the pregnancy if they chose to do so. The amniotic fluid is examined by the laboratory and it will help to diagnose certain abnormalities of the fetus.

An amniocentesis is usually recommended by the physician because the mother is over thirty five years old, one or both of the parents have a chromosomal abnormality or if the mother has given birth to a child with Down Syndrome in the past. Someone with other family related concerns or pregnancy concerns can request that one be performed. It is usually an outpatient procedure that is done in the hospital or surgery center.

The procedure is guided by ultrasound. This way, the physician can see where the needle is going and can avoid the fetus. A local anesthetic is used to minimize any pain to the patient. A hollow needle is inserted through the abdominal wall into the uterus. A small amount of the amniotic fluid is suctioned out through the needle and then the needle is removed. It is usually a very quick procedure, as long as the fetus is cooperating.

One health problem that an amniocentesis can detect is Down Syndrome, or Trisomy 21. This is mental retardation that also affects many of the organs. Some signs of Down Syndrome that are seen after birth is the lack of normal muscle tone, head and face abnormalities, almond shaped eyes, broad hands with large palm creases and a heart murmur. Later in life, the child will have slower growth and development and mental retardation. This is caused by an extra chromosome in the fertilized egg. The risk increases with pregnant women under the age of sixteen and over the age of thirty five. There is also an increase if there is a family history of Down Syndrome.