No, there was not a switch made at the hospital. As explained above, there is no way that Michael and Danielle could have had a child with Type O blood, but it is possible for Earnest andDenise to have a child with Type O blood. Even though Earnest has Type A blood and Denise hasType B blood, it is possible that they each contain one i allele, Earnest could have the IAi combination and Denise could have the IBi combination. If each of them gave their i allele to their child, then the child would end up with Type O blood.