Health & Pregnancy

How It Is Done

A genetic test can be done using almost any cell or tissue from the body.

Blood sample from a heel stick

If genetic testing is done on a baby, a heel stick will be done instead of a blood draw from a vein. For a heel stick blood sample, several drops of blood are collected from the heel of the baby. The skin of the heel is cleaned with alcohol and then pricked with a small, sterile lancet. Several drops of blood are collected inside circles on a specially prepared piece of paper. When enough blood has been collected, a gauze pad or cotton ball is placed over the puncture site. Pressure is applied to the puncture site briefly, and then a small bandage is usually placed over it.

Blood sample from a vein

The health professional drawing your blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.

Cell sample from a fetus

For this type of testing, cells are collected from the fetus using amniocentesis or chorionic villus sampling. For more information about amniocentesis, see the topic Amniocentesis or Chorionic Villus Sampling.

How It Feels

Blood sample from a heel stick

The baby may feel a brief sting or a pinch when the lancet pricks the skin. While the blood is being collected, there is very little or no discomfort.

Blood sample from a vein

You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. But many people do not feel any pain, or have only minor discomfort, once the needle is positioned in the vein. The amount of pain you feel depends on the skill of the health professional drawing the blood, the condition of your veins, and your sensitivity to pain.

The collection of DNA from saliva, urine, or semen does not cause discomfort.

Risks

Blood sample from a heel stick

There is very little risk of complications from having blood drawn from a heel stick. A small bruise may develop at the puncture site.

Blood sample from a vein