Through surveys of urban and rural couples who have given birth to children, we found that some concepts and behaviors of young couples have a great impact on the physical quality of their offspring. Misunderstanding 1: If you are in good health, you do not need a premarital check-up. More than half of the young people of childbearing age believe that they are in good health and do not need a pre-marital check-up. But in fact, some young men and women who appear to be healthy and whose parents are also healthy are actually carriers of the disease-causing gene. If both men and women happen to be carriers of a certain disease-causing gene, the probability of their offspring getting the disease is very high. Due to hereditary or sporadic genetic diseases, both men and women often have only the disease-causing gene