In fact, prevention of rare disorders is difficult, especially in the case of genetic disorders involving a recessive gene. Only when a child is born with such a disorder is it revealed that both parents are symptomless carriers of the defective gene in question.
事實上，罕見疾病的預防有其困難，特別是隱性遺傳疾病，只有生下罹病的孩子時，才知道父母雙方都是無症狀的隱性帶因者。