Important Facts About the Amniocentesis

An amniocentesis (or simply "amnio"), is a prenatal test very similar to the chorionic villus sampling test in that it is performed on pregnant women to identify various genetic disorders, including Down Syndrome. The test is usually done between 16 and 20 weeks of pregnancy.

Under what circumstances should the test be taken?

The amniocentesis is generally offered to pregnant women who are age 35 and older, as this increases their chances of birthing a baby with chromosomal defects. It may also be offered to diagnose or rule out a uterine infection, determine whether the baby's lungs are mature enough for an early delivery if the mother appears to be in premature labor or require an early delivery for any reason, or monitor the health of a baby if the mother has Rh sensitization - a complex condition that can occur if the mother has Rh negative blood and the baby has Rh positive blood.

How is the test performed?

The test is typically performed in a doctor's office while lying on an examination table. First, the mother's belly is cleaned with an antiseptic solution. Next, guided by ultrasound, the doctor inserts a thin, hollow needle through the abdomen wall and into the uterus. The ultrasound helps to locate a pocket of amniotic fluid that is a safe distance between the baby and the placenta. Two to four teaspoons of amniotic fluid is withdrawn into a syringe, and the needle is removed. It usually takes less than 30 seconds to withdraw the fluid, but it can take up to a few minutes. During the procedure the mother may feel cramping, pinching, or pressure on the abdomen. Some mothers even report having no discomfort at all. One may choose to receive a local anesthetic to numb the abdomen prior to the procedure; however, this is likely to cause more pain than the procedure itself.

What are the risks?

Cramping, leakage of amniotic fluid (< 1% of women), light vaginal bleeding (< 3% of women), needle injury to the baby if it moves into the needle's path, Rh sensitization, or miscarriage. It is estimated that between one and 400 women will miscarry; although, there seems to be no real scientific consensus on the actual risk of miscarriage due to the amniocentesis.

What else should I consider?

> Although the amniocentesis accurately identifies certain genetic disorders such as Down Syndrome, it can't identify all birth defects.

> The risk of a false positive is less than 1% when maturity amniocentesis (performed after 36^th week of pregnancy) indicates that the baby's lungs are mature enough for birth.

> Speak with your doctor or genetic counselor to address all questions and concerns. This is a very personal and sensitive decision, and there is no 100% right or wrong way to go on this matter.

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