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A 40-year-old member asked:

Can a child have a negative blood type if both of her parents are o positve?

2 doctor answers6 doctors weighed in
Dr. David Galbraith
Pediatrics 48 years experience
Yes: Each parent has two rh genes. It only takes one positive gene to make a person rh positive, so each parent can have a positive and a negative rh gene. Both genes have to be rh negative for someone to be rh negative. Since each parent only contributes one gene to child, the child can get a negative gene from each parent and therefore be rh negative.
Dr. Richard Pollard
Anesthesiology 30 years experience
Maybe: Rhesus transmission (+ or -) is not a clear as the ABO transmission. It is also separate from the genetics for "blood type". This is purely a result of the genetic expression of each parent, and this may be different when their genes are combined in a new child.

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A 48-year-old member asked:

Is it possible to have both parents with o positive bloodtype, but their child have o negative blood type?

2 doctor answers4 doctors weighed in
Dr. James Ferguson
Pediatrics 46 years experience
Yes: The rh factor is inherited through separate genetic means from the blood type. The rh factor is a dominant gene, meaning only one gene is needed to cause expression of the factor. So two rh + parents can have a rh+/rh- gene pattern and have a 1/4 chance with every conception of having an rh-/rh- baby, 1/4 chance of rh+/rh+ baby and 1/2 of carrier rh+/rh-.
FL
A 44-year-old female asked:

Can a child have different blood type than their parents, if one has A+ and O-?

1 doctor answer4 doctors weighed in
Dr. Stuart Janousky
Pediatrics 37 years experience
Blood type: Your child should be either A or O. Not B or AB. They could be either positive or negative however.
A 41-year-old member asked:

How often do blood type a- and o+ parents have a+ offspring?

1 doctor answer1 doctor weighed in
Dr. Holly Maes
Pediatrics 36 years experience
Absolutely: An 'a neg' person can be ao or aa for the 'a' and must be negative/negative for the rh. So they can give an a or an o gene, but must give a negative rh gene. The 'o' blood type is only oo genetically, but positive/positive or positive/negative for the rh gene. So if the a gives an a and a negative, and the o gives an o and a positive, the child will be a positive, because these are both dominant.
Philippines
A 23-year-old male asked:

Can an ab and o blood type parents have o blood type child?

1 doctor answer2 doctors weighed in
Dr. Nayla Mumneh
Allergy and Immunology 29 years experience
Unlikely: A and b are more dominant.
Dr. Ed Friedlander
Pathology 44 years experience
Mendel's laws allow a classic O and a classic AB parent to have children with type A or type B, but not type O or type AB. Rare alleles could allow this to happen. If there is any question about the child's paternity, get it resoved using 21st century methods.
Feb 20, 2013
A 43-year-old member asked:

If both parents have o+ blood type can their child have a+?

2 doctor answers4 doctors weighed in
Dr. James Ferguson
Pediatrics 46 years experience
If they adopt one: The genetics of blood groups is rather straight forward. The only way to pick up a a gene is to have one in the donor.I find an occasional adult who actually doesn't know their blood type or was told the wrong type in the past. The days of getting a blood transfusion based on history or even recorded on your dog tags is long gone. Too much risk of transfusion rxn. All are rechecked at time of need.

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Last updated Jan 24, 2017
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