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Indirect Coombs Test

Topic Overview

An indirect Coombs test can be used to determine whether there are antibodies to the Rh factor in the mother's blood. In this case:

  • A normal (negative) result means that the mother has not developed antibodies against the fetus's blood. A negative Coombs test indicates that the fetus is not presently in danger from problems relating to Rh incompatibility.
  • An abnormal (positive) result means that the mother has developed antibodies to the fetal red blood cells and is sensitized. However, a positive Coombs test only indicates that an Rh-positive fetus has a possibility of being harmed. A positive test cannot indicate the amount of fetal harm that has occurred or is likely to occur.

If test results show that antibody amounts are increasing during pregnancy, the fetus may be at greater risk of harm.

A fetus who is Rh-negative will not be harmed, even if the mother is sensitized.

Related Information

Credits

Current as of: February 11, 2020

Author: Healthwise Staff
Medical Review: Sarah Marshall MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Kathleen Romito MD - Family Medicine
Elizabeth T. Russo MD - Internal Medicine
Kirtly Jones MD - Obstetrics and Gynecology

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