Definition

Amniocentesis is a prenatal diagnostic test performed by taking a small sample of amniotic fluid out of the uterus through a needle to test the baby for chromosomal abnormalities.

Who is amniocentesis recommended for?

• Are pregnant and over the age of 35
• Have a family history of genetic problems
• Had other tests that indicate the fetus may have health problems
• Already have children with birth defects
• Have a chromosome abnormality
• Have a different blood type than their baby
• Will have an early delivery and need to check if the baby's lungs are developed

What are the benefits of the procedure?

• Unlike Chorionic Villus Sampling, an amniocentesis can test for neural tube defects, such as spina bifida
• It can detect nearly all chromosomal abnormalities, including Down Syndrome and sex chromosome abnormalities
• The detection rate for chromosomal abnormalities is over 99% and it can rule out between 98-99% of open neural tube defects.

What is an Amniocentesis?

An amniocentesis is a prenatal test that is completely voluntary. The patient will meet with a genetic counselor prior to the procedure to discuss the risks and benefits of an amniocentesis. Ultimately, the patient decides whether or not she would like to have the procedure. The test is typically done between the 15th and 24th week of pregnancy. The test does not require an overnight stay for the patient.

To perform the procedure the doctor uses an ultrasound to determine the location of the placenta and the baby. A fine needle is then inserted in the patient's abdomen, through the uterus, and into the amniotic sac. The needle extracts about 1-2 tablespoons of the amniotic fluid that surrounds the baby. The baby will easily produce more amniotic fluid to replace the fluid that is extracted. The cells in the amniotic fluid have the same genetic makeup as the baby.

The sample of amniotic fluid is tested for genetic disorders or chromosomal abnormalities. The doctor studies the number and shape of the chromosomes within the extracted sample. The results of the sample are usually available within seven to ten days after having the procedure.

Overall, most women do not describe the procedure as being painful. Some women describe discomfort in the abdominal areas, similar to menstrual cramps. Some women may experience some mild cramping for a few hours after the procedure.

After the procedure, the patient needs to call her doctor if she experiences:

• Excessive bleeding
• Loss of amniotic fluid vaginally
• Fever
• Severe cramping
• Infection

There is a very small risk of having a miscarriage after the procedure.

Rehabilitation

Patients should avoid heavy lifting and strenuous activity for 2-3 days after having the procedure. Patients should plan on relaxing for the rest of the day after the procedure.

1/20/2009