Conditions + Treatments

Amniocentesis In-Depth

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When do I need amniocentesis?

Amniocentesis is performed to detect certain birth defects such as Down syndrome,sickle cell disease, cystic fibrosis, muscular dystrophy and Tay-Sachs, among others. It can also detect neural tube defects (diseases in which the brain and spinal column don't develop properly), such as spina bifida and anencephaly. The procedure is 99.4 percent accurate.

The procedure is generally performed on women who will be older than 35 years when they give birth, since these women have a higher risk of delivering a baby with chromosomal abnormalities. The procedure is also given to women who have had an abnormal ultrasound or blood screen, have a family history for certain birth defects and have another child with an inherited disorder.

How is amniocentesis performed?

Amniocentesis is an outpatient procedure. It involves inserting a long, thin needle through the mother’s abdomen and into the amniotic sac to withdraw a small sample of fluid. The fluid inside the sac contains substances that provide important genetic information about your baby’s health.

First, your abdomen is cleaned with an antiseptic. You may receive a topical numbing medication or a local anesthetic injected into the skin. Then, the doctor inserts a needle which is guided by ultrasound, into the amniotic sac. The ultrasound allows the doctor to see the exact location of the baby. Finally, a small sample of fluid (less than 1 ounce) is withdrawn for laboratory analysis. 

You may have cramps similar to menstrual cramps during the procedure or for a few hours afterward. It’s recommended that you avoid strenuous activities, including exercise, for the next 24 hours.

Are there any risks to having the procedure?

A genetic counselor will discuss the risks and benefits of having the procedure with you. You can choose whether to go through with amniocentesis.

In general, there risks are minimal. There is a less than 1 percent risk, or 1 in 200 to 1 in 400 pregnancies, of miscarriage. Preterm labor or injury and infection to the baby or the mother are extremely rare but can occur. The procedure can also lead to leaking amniotic fluid and vaginal bleeding.

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