Your Baby’s Health and Amniocentesis

Every pregnant woman has questions and concerns about her baby’s health. Many factors, including age and your medical and family history, play an important role. While most babies are born healthy, unfortunately 2% to 5% are born with birth defects.

Woman’s Hospital’s Maternal-Fetal Medicine Center offers prenatal diagnostic tests, such as ultrasound-guided amniocentesis, which can help detect birth defects. Your Woman’s doctor or genetic counselor can answer all your questions and help you decide if amniocentesis is for you.

What Is amniocentesis?

Amniocentesis is a test that has been available for more than 20 years.  The procedure is usually performed 15 to 20 weeks after your last menstrual period, when you are about 4 to 5 months pregnant.

The doctor then inserts a needle through your abdomen into a pocket of amniotic fluid. A small sample of the amniotic fluid (which contains cells from the fetus) is taken. This usually takes just a few minutes and is relatively painless. Some women describe feeling a “pinch” and then some pressure, while other women experience no discomfort at all.

Is there any risk associated with amniocentesis?

There is always a natural risk of miscarriage during pregnancy. Amniocentesis increases the normal risk of miscarriage by 0.5%, meaning that fewer than 1 in 200 women will miscarry because of the amniocentesis.

What problems can amniocentesis detect and who should consider having it?

You should consider having amniocentesis if you are 35 years of age or older at delivery; if you have a child or other relative with a chromosome abnormality (such as Down syndrome) or a detectable genetic disorder (such as thalassemia or muscular dystrophy); if you have had an abnormal blood screening; or if you have a child or other relative with a neural tube defect (such as spina bifida).

How accurate are the results and how long does it take to receive them?

While results from these tests are highly accurate, no method of prenatal testing can guarantee that a baby will be born without birth defects, genetic disease or mental retardation. However, there is a high degree of accuracy:

•    The chromosome results are more than 99% accurate

•    The AFP measurement detects 90 to 95% of neural tube defects

•    The DNA and enzyme studies are also highly accurate

Usually, the test results are ready in 10 to 14 days. Special studies may take longer. After amniocentesis, most women are able to return to their normal activities within one to two days following the procedure. Some women experience mild cramping and spotting after the test, which usually resolves without further complication.

The Maternal-Fetal Medicine Center is staffed by highly qualified, board-certified doctors and genetic counselors who specialize in prenatal diagnosis. The center is located on the third floor of the Physician Tower I building.