General Information

Definition. Amniocentesis is the removal of fluid from the amniotic sac (bag of waters) during pregnancy.

Description of Procedure

The main objective of amniocentesis is to obtain amniotic fluid from within the uterus, using a hollow needle carefully inserted into the abdomen. The surgeon will first inject a local anesthetic into the skin where the needle will be inserted. The hollow needle measures about 3 1/2 inches in length. It will be inserted into the skin of the abdominal wall, then through the muscle layer of the uterus, and into the cavity of the uterus. A small amount of fluid - less than an ounce - will then be removed by suction to send to the laboratory for examination. The needle will cause some pain when it penetrates the uterus, but the pain should not last long and should not hurt worse than any injection into any other part of your body. After the fluid removal has been accomplished, the removal of the needle should cause no further discomfort. 

Simultaneously during the procedure, ultrasonography (a harmless and painless procedure using high-amplitude sound waves to outline objects inside the body) provides guidance for the needle, to prevent it from harming the unborn child. Ultrasonography also provides new, additional information. Major malformations of the fetus, the presence of twins, and the age of the fetus can be determined from the screen that reflects the image of the ultrasound waves.

When amniocentesis is being performed to diagnose possible congenital abnormalities, most authorities recommend doing it between the 15th and 18th weeks of pregnancy. At this time there is ample fluid available for testing and enough time remaining for termination of the pregnancy if you and those closest to you decide on that course.

Occassionally, amniocentesis is performed in late pregnancy, to determine maturity and other conditions of the unborn child.

Try to be calm and relaxed before the procedure. Sedative and pain medicines, which may be customary before other minor surgical procedures, will be withheld in this one to ensure the safety of the unborn child.
 

Laboratory Studies

The laboratory will preform the following studies on the sample of amniotic fluid:

• The alpha-fetoprotein level in the amniotic fluid will be checked. An elevation beyond normal limits may suggest one of several abnormalities, such as failure of the spinal cord to close, failure of the abdomen to close, or obstruction in the gastrointestinal or urinary systems.
• Cells, which are always present in amniotic fluid, will be collected and grown in tissue-culture to check them for abnormalities of the chromosomes.
• Biochemical tests will be preformed that can identify about 70 inborn errors of metabolism.
• Biochemical (L/S ratio) testing will determine maturity of the fetus.

Safety and Risks

In the medical literature, authors give varying estimates of the risks of amniocentesis. Some estimate that 1 out of every procedures will initiate an unwanted abortion of the pregnancy. Others report much less of a risk, such as 1 in 150. But you should be aware of this risk, to help you decide whether to have the procedure performed or not. It is also best to discuss the risks with your doctor and determine the necessity of the procedure.
 

Situations That May Justify the Risk

• Birth of a previous child with a chromosome abnormality (such as Down's syndrome)
• Mother's age is over 35 years
• Either parent with a known chromosome abnormality
• Mother known to carry a sex-linked abnormality (such as hemophilia, which affects only sons). In this case, the real purpose of the amniocentesis would be to establish the sex of the unborn child.

The vast majority (over 95 percent) of tests performed in amniocentesis disclose no abnormalities. Some couples at high risk may desire to have the procedure done so that they will be less anxious during the pregnancy, if the tests show no abnormalities. However, a normal amniocentesis cannot guarantee a normal child - we have no way at present to test for all abnormalities. If the tests do disclose an abnormality, and you decide not to terminate the pregnancy, then the procedure will enable you to plan for the future and to look for ways to help you cope.
 

Important Points for Postprocedure Care

Activity
You should be able to return to all your normal activities within a few hours after the procedure. Stay as active as your general health and feelings of well-being allow.

Diet
There are no dietary restrictions relating to the procedure.

Medications
You will be given no medications following the procedure.

General Measures
You may shower or bathe as usual right away.

• Don't smoke cigarettes
• Continue to avoid all drugs and alcoholic beverages

Call Our Office If:

• You get a fever
• You feel nauseated and you vomit
• You experience pain in the shoulder
• You notice vaginal bleeding

Disclaimer: The articles and information, while with the best effort to be accurate and up-to-date, may not be. Also, every physician and medical professional holds their own views on certain diagnosis and advice. There truly are no textbook cases. It is always best to consult with your personal physician regarding medical/health related problems. The information is to be used as a general resource and not as a substitute for trained medical advice and/or treatment.