Certain birth defects and syndromes are polygenetic in nature. typically, the chance that an offspring will be born with a polygenetic affliction is small. however, once an offspring is born with the affliction, the probability that future offspring of the same parents will be born with the same affliction increases. let's assume that the probability of a child being born with affliction a is 0.003. if a child is born with this affliction, the probability of a future child being born with the same affliction becomes 0.06.