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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.
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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.
You do not need to do anything before you have this test.
The health professional drawing blood will:
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.
There is very little chance of a problem from having a blood sample taken from a vein.
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.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.
Things that may affect your test results include:
The results of the quad screen, including inhibin A, take into account a woman's age, race, weight, and whether she has diabetes.
CitationsPagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.Other Works ConsultedFischbach 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.
Current as of: February 11, 2020
Author: Healthwise StaffMedical Review: Sarah Marshall MD - Family MedicineBrian D. O'Brien MD - Internal MedicineE. Gregory Thompson MD - Internal MedicineAdam Husney MD - Family MedicineKathleen Romito MD - Family MedicineSiobhan M. Dolan MD, MPH - Reproductive Genetics
Current as of: February 11, 2020
Author: Healthwise Staff
Medical Review:Sarah Marshall MD - Family Medicine & Brian D. O'Brien MD - Internal Medicine & E. Gregory Thompson MD - Internal Medicine & Adam Husney MD - Family Medicine & Kathleen Romito MD - Family Medicine & Siobhan M. Dolan MD, MPH - Reproductive Genetics
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