If both husband and wife have O blood type, the child must be born with O blood type. The blood type of the child after birth is genetically determined by both parents, because the gene of blood type O is recessive, and the child born with two recessive parents is still recessive, so it is still blood type O. If one parent has O blood type and the other parent has A blood type, the child born can be A or O blood type. If the other parent has B blood type, the child born can be either B or O. If the other party is of blood type AB, the child born can be of blood type A, B or AB. If the mother has type O blood and the father has type A, B or AB blood, the child is prone to jaundice after birth, and in some cases hemolysis occurs during pregnancy resulting in miscarriage. The mother needs to check the antibody potency during pregnancy and the child needs to be aware of jaundice after birth.