Test Overview

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 22 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.

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.

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How To Prepare

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

A normal result means that the level of the hormone inhibin A is low, or negative. An abnormal result means the level of the hormone inhibin A is high, or positive.^{footnote 1} The level of the hormone must be reviewed with the quad screen blood tests.

All abnormal results will need to be discussed with your doctor.