What you can expect

By Mayo Clinic Staff

Before week 24 of pregnancy, cordocentesis is usually done in an outpatient facility or the health care provider's office. After week 24 of pregnancy, cordocentesis is usually done in the hospital. At least one assistant will likely help your health care provider during the procedure.

A sample of your blood will be taken before the procedure for comparison with the fetal blood samples.

During the procedure

About 30 to 60 minutes before the procedure, you might be given antibiotics to reduce the risk of a uterine infection. This is usually done through an intravenous catheter.

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 A small amount of blood from the vein in the umbilical cord will be withdrawn into a syringe, and the needle will be removed.

You'll need to lie still while the needle is inserted and the blood is withdrawn.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.

After the procedure

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

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

When you 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. Your health care provider will ask you to contact him or her if you experience signs or symptoms such as vaginal bleeding or fluid leaking.

Meanwhile, the blood sample will be analyzed in a lab. Test results are typically available within days.

Oct. 08, 2015