Your baby's health and amniocentesis

Every pregnant woman has questions and concerns about her baby's health. Many factors, including age, genetic, medical and family history, play an important role. While most babies are born healthy, unfortunately a few are born with birth defects.

Kapi'olani Medical Center for Women & Children offers prenatal diagnostic tests, such as amniocentesis, which can help detect birth defects.

Below are answers to some of the most common questions about amniocentesis. If you decide to have this test, your doctor or genetic counselor will answer any other questions you may have.

What is amniocentesis?

Amniocentesis is one method of prenatal diagnosis checking the health of the fetus (unborn baby). It has been available to women for more than 20 years. The procedure is usually performed 15-20 weeks after your last menstrual period (when you are about 4-5 months pregnant). First, an ultrasound examination locates the placenta, the fetus, and the amniotic fluid surrounding the fetus. A needle is then inserted through the abdomen into a pocket of amniotic fluid and a small sample of fluid is taken. The procedure usually takes just a few minutes.

The amniotic fluid contains cells from the fetus. These cells are allowed to grow in special lab conditions for several days. A specific protein in the fluid called, Alpha Fetoprotein (AFP), is also measured.

What problems can it detect?

• Careful study of the cells will identify chromosome problems, such as Down Syndrome.
• Measurement of the AFP will detect the majority of neural tube defects, such as spina bifida.
• When a history of genetic disorder is known in a family, specific testing may be available through DNA or enzyme analysis.

No method of prenatal testing can guarantee that a baby will be born without birth defects, genetic disease or mental retardation.

Who should consider amniocentesis?

Women should consider amniocentesis if they:

• Are 35 years of age or older at delivery.
• Have a child or other relative with a chromosome abnormality, such as Down Syndrome.
• Have a child or other relative with a detectable genetic disorder, such as Thalassemia or Muscular Dystrophy.
• Have an abnormal blood test (e.g. TripleMark).
• Have a child or other relative with a neural tube defect, such as spina bifida.

How accurate are the results?

• The chromosome results are more than 99% accurate.
• The AFP measurement detects 90-95% of neural tube defects.
• The DNA and enzyme studies are also highly accurate.

Occasionally, test results need to be clarified through additional ultrasound examinations or blood tests on both parents. Rarely, is a repeat amniocentesis needed.

How long does it take to get results?

Results of the chromosome study and AFP measurement are usually available in two weeks. Special studies may take longer.

Is the procedure painful?

Most women describe feeling a pinch and then some pressure, similar to having blood drawn. Other women experience no discomfort at all.

What should I expect after amniocentesis?

Generally, women are able to return to their normal activities following amniocentesis. Some women experience mild cramping and spotting after the test, but this usually resolves without further complication. If you elect to have amniocentesis, you will receive more information on what to expect following the procedure.

Is there any risk with amniocentesis?

Throughout pregnancy, there is always a natural risk of miscarriage. Amniocentesis increases the normal risk of miscarriage by 0.5%. It means less than one in 200 women would have a miscarriage as a result of amniocentesis.

What special preparation is required?

Unlike some other prenatal diagnostic tests, you will not need a full bladder for the test. You may eat and drink before the procedure. Please wear comfortable clothing. Be prepared to answer questions about your family's health history.

Why choose Kapi'olani Medical Center for prenatal testing?

The Fetal Diagnostic Center at Kapi'olani Medical Center for Women & Children is staffed by highly qualified, board-certified doctors and genetic counselors who specialize in prenatal diagnosis. Call the Fetal Diagnostic Center at 983-8559.

We hope this information has answered most of your questions about amniocentesis. Your genetic counselor will explain this information in greater detail and will assess your individual risks during your counseling session. To schedule an appointment, please call your physician. Meanwhile, take a few moments to write down any questions or concerns you have and bring them with you to your counseling session. We look forward to meeting with you.

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