Does anyone know whether two people with A+ blood types can produce a child with 0+ blood type?

Hello jranderson.

To have a blood type of A+, that means your blood type is either AA or Ao

Therefore, it is possible for 2 people with A+ blood types to produce a child with O+ blood type.

See this Matrix.

MOM AA or Ao
DAD
AA-->AA-->AA or Ao
or
Ao-->AA or Ao ->AA or Ao or oo

Therefore, if 2 people who both have A+ blood types have a child, their child's blood type must be either AA or Ao or oo

To make it a little simple,
A child with blood group O can ONLY be a result if both parents are of blood group A, genotype AO (not AA)

A O
A AA AO
O AO OO

Also see this link! - http://www.craigmedical.com/blood_typing_facts.htm

you I think they can
u see
both r A+ marries A+= the nkids can be ,now there r 4 posibilities

AA,A+,A+,or ++ (O+)
well the probability of this kid being O+ is juts 1/4
but still it's there...

Wouldn't it be 1/3 since you have A+ twice?

You 1/3