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Wednesday, September 17, 2014
Inherited Disorders and Birth Defects
My wife and I have positive RH. Can we have an RH neg child?
Yes. The Rh proteins are arranged into 2 groups - either positive or negative. Each person has two forms (called alleles) of the Rh gene. One is the positive form (that is, the allele is positive or +) and the other is the negative form (the allele is negative or -).
People with 2 positive alleles (++) are Rh positive; people with one positive allele and one negative allele (+ -) are also Rh positive. People with 2 negative alleles (- -) are Rh negative.
Of the different combinations people can have - if both parents are Rh positive they may be either ++ or + -. If both Rh positive parents are + -, they have a 25% chance of both passing on the negative allele (-) at the same time to a child. This child would have 2 negative alleles (- - ) and would be Rh negative.
Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University