Amniocentesis

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Definition | Body Parts Involved | Reasons for Procedure | Complications | What to Expect | Outcome | Call Doctor If

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Definition

Removal of fluid from the amniotic sac during pregnancy

Parts of the Body Involved

Uterus, amniotic sac

Reasons for Procedure

The removal and laboratory examination of amniotic fluid helps to diagnose abnormalities in an unborn child. Amniocentesis is usually done between the 14th and 20th weeks of pregnancy, when there is enough amniotic fluid available for testing purposes. Cells from the amniotic fluid are grown in the laboratory for 1 to 2 weeks, and are then tested for chromosomal disorders or various birth defects.

Amniocentesis is most often performed for the following reasons:

• Mother is over 35 years old
• Either parent has a chromosomal abnormality
• Mother has previously given birth to a child with a chromosomal abnormality, such as Down syndrome
• To determine whether the baby's lungs are mature
• Mother has abnormal results from blood screening test such as maternal serum alpha-fetoprotein (AFP)

Risk Factors for Complications during the Procedure

• Obesity
• Previous abdominal surgery
• Previous infection in pelvic organs

What to Expect

Prior to Procedure - Blood and urine tests

During Procedure - Ultrasound, anesthesia

Anesthesia - Local by injection (optional)

Description of the Procedure - You will lie on an examining table. Ultrasound is used to see exactly where the fetus and the placenta are located. This allows the doctor to choose a safe spot for inserting the amniocentesis needle. Your abdomen is cleaned, the needle is inserted through your abdomen into your uterus, and a few teaspoons of amniotic fluid are withdrawn. After the needle is removed, the doctor again uses ultrasound to ensure that the fetal heartbeat is normal.

How Long Will It Take? Locating the fetus and inserting the needle can take up to 20 minutes; withdrawing the fluid takes 5 minutes. You will be asked to remain on the table for an additional 15 or 20 minutes to relax.

Will It Hurt? You may feel some cramping or pressure when the needle enters the uterus or during the few minutes that fluid is being withdrawn.

Possible Complications:

• Excessive bleeding
• Surgical wound infection
• Slight risk of miscarriage (risk increases if procedure is done during first trimester rather than during the second trimester)

Average Hospital Stay - None

Postoperative Care:

• Rest for 24 hours after the procedure
• Bathe and shower as usual
• No heavy exercise or sexual relations for 24 hours

Outcome

Your results will be available within 10-14 days. Although more than 95% of women who undergo amniocentesis will test negative for fetal birth defects, no prenatal test can guarantee the birth of a healthy baby because not all birth defects can be ruled out prenatally. Amniocentesis, however, has an accuracy rate of between 99.4% and 100% in diagnosing chromosomal abnormalities, such as those that cause Down syndrome and trisomy 18.

Call Your Doctor If Any of the Following Occurs

• Signs of infection, including fever and chills
• Nausea or vomiting
• Pain or cramping in the lower abdomen or shoulder
• Vaginal bleeding or a loss of fluid from the vagina
• Redness, swelling, increasing pain, excessive bleeding, or discharge from the amniocentesis site
• New, unexplained symptoms

SOURCES:

American Academy of Obstetrics and Gynecology

March of Dimes

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Last reviewed January 2001 by Medical Review Board