What you can expect

By Mayo Clinic Staff

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Cordocentesis is usually done in an outpatient facility or the health care provider's office, but in some cases it might be done in the hospital. At least one assistant will likely help your health care provider during the procedure.

During the procedure

About 30 to 60 minutes before the procedure, you might be given antibiotics to reduce the risk of a uterine infection.

When the procedure begins, your health care provider will use ultrasound to determine the baby's exact location in your uterus. You'll lie on your back on an exam table, and your health care provider will apply a special gel to your abdomen. He or she will then use a small device known as an ultrasound transducer to show your baby's position on a monitor.

Next, your health care provider will clean your abdomen with an antiseptic. Sometimes local anesthetic is used to ease discomfort during the procedure, but often it isn't needed.

Guided by ultrasound, your health care provider will insert a thin, hollow needle through your abdominal wall and into your uterus. A small amount of blood from the vein in the umbilical cord will be withdrawn into a syringe, and the needle will be removed.

You'll need to lie still while the needle is inserted and the blood is withdrawn. You might notice a stinging sensation when the needle enters your skin, and you might feel cramping when the needle enters your uterus.

The entire procedure usually takes about an hour, although most of that time is devoted to the ultrasound exam.

Your baby will naturally replace the small amount of blood that's removed.

Rarely, a blood sample can't be taken from the umbilical cord. In these cases, a blood sample might be taken from a vein in the baby's liver.

After the procedure

After the blood sample is taken, you might experience cramping or a small amount of vaginal bleeding.

Your health care provider might use ultrasound or an external labor monitor to track your baby's heart rate for an hour or two after the procedure.

When you're allowed to go home, your health care provider might suggest resting for the remainder of the day. You'll likely be able to resume normal activities the next day.

If you experience fever, chills or vaginal bleeding, contact your health care provider right away.

Meanwhile, the blood sample will be analyzed in a lab. Test results are typically available within a matter of days — or in some cases, within a matter of hours.

Oct. 13, 2012