The English word sperm (sperm) comes from the ancient Greek word sperma, which originally meant seed. So, people would compare having children to sowing seeds in the land, where the land is the woman’s womb and the seeds are the man’s sperm. Men can produce sperm continuously from their teens to their oldest years. From this point of view, men have a longer reproductive life than women, even to 70 or 80 years old, still has the function of reproduction. Women are different. After menopause, the ovaries shrink and no more eggs are produced, so basically, they can’t have children. However, although theoretically men have the ability to reproduce at the age of eighty, the older they are, the more the number and vitality of sperm will decline and the number of deformed sperm will also increase. From the point of view of eugenics, men in the 25-35 years of age this stage of reproductive capacity is the most vigorous, after 35 years old, reproductive capacity will begin to go downhill. In middle age, the number of sperm that can “sprint” decreases at a rate of 3.1% per year: between the ages of 20 and 29, about 90% of the sperm cells are contained in the varicocele; between the ages of 40 and 50, it drops to 50%. In addition, sperm motility decreases at a rate of 0.7% in middle age, and the number of sperm that can “swim” and “sprint” decreases at a rate of 3.1% per year. There is a relationship between the father’s reproductive age and the occurrence of congenital dysmorphism, and it is even believed that 25% of congenital dysmorphism is caused by the father’s side. Therefore, from the perspective of eugenics, it is not advisable to have children too late. Considering various factors such as work, health, financial strength, physical strength and energy in favor of future parents, men try to have their second child before the age of 40, otherwise they will face a high risk of childbirth.