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Hormone Inhibin A

The inhibin A test is done to measure the amount of this hormone in a pregnant woman's blood to see if the baby may have Down syndrome. Inhibin A is made by the placenta during pregnancy.

The level of inhibin A in the blood is used in a maternal serum quadruple screening test. Generally done between 15 and 20 weeks, this test checks the levels of four substances in a pregnant woman's blood. The quad screen checks alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), a type of estrogen (unconjugated estriol, or uE3), and the hormone inhibin A. The levels of these substances—along with a woman's age and other factors—help the doctor estimate the chance that the baby may have certain problems or birth defects.

Pregnancy: Should I Have the Maternal Serum Triple or Quadruple Test?

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Pregnancy: Should I Have Screening Tests for Birth Defects?

Why It Is Done

A test for inhibin A is done in addition to other tests to see if there is a chance of chromosome problems, such as Down syndrome.

How To Prepare

You do not need to do anything before you have this test.

How It Is Done

The health professional drawing 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.
  • Put a gauze pad or cotton ball over the needle site as the needle is removed.
  • Put pressure on the site and then a bandage.

How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

You may feel anxious while awaiting results of a maternal serum quad test done to determine the health of your unborn baby.

Risks

There is very little chance of a problem from having blood sample taken from a vein.

  • You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
  • In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
  • Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

WebMD Medical Reference from Healthwise

Last Updated: April 04, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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