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Hormone Inhibin A

Results

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

A normal result means 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.1 The level of the hormone must be reviewed with the other quad screen blood tests.

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

What Affects the Test

Things that may affect your test results include:

  • If you smoke. This may increase the level of inhibin A in the blood.
  • If you are obese. This may decrease the level of inhibin A in the blood.

The results of the quad screen, including inhibin A, take into account a woman's age, race, weight, and whether she has diabetes.

What To Think About

  • The maternal quad screen looks for possible problems in your developing baby (fetus). You can have an ultrasound if your quad screen is abnormal. If an ultrasound cannot find the cause of the abnormal results, an amniocentesis may be recommended. For more information, see the topic Fetal Ultrasound or Amniocentesis.
  • If abnormal levels of inhibin A are found, talk with your doctor or a genetic counselor. The test results can be abnormal, even when nothing is wrong.
  • The level of inhibin A in the blood is often used in a maternal serum triple or quadruple screening test. For more information, see the topic Triple or Quad Screening for Birth Defects.

Citations

  1. Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

Other Works Consulted

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

  • Wapner RJ, et al. (2009). Prenatal diagnosis of congenital disorders. In RK Creasy et al., eds., Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice, 6th ed., pp. 221–274. Philadelphia: Saunders Elsevier.

ByHealthwise Staff
Primary Medical ReviewerSarah Marshall, MD - Family Medicine
Specialist Medical ReviewerSiobhan M. Dolan, MD, MPH - Reproductive Genetics
Last RevisedApril 4, 2012
1|2

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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