What is the most appropriate age to have children? When advocating for late marriage and eugenics, it is inevitable that the best age for childbirth will be considered. The Marriage Law stipulates that men can only get married at the age of 22 and women at the age of 20, which is the minimum legal age for marriage. This is not the same as the most suitable age, let alone the best age for childbirth, because the age of marriage and the age of childbearing are two different things. In terms of physiology, men begin to enter puberty at the age of 16, when the testicles mature and begin to produce sperm have the ability to reproduce, after the age of 50 fertility gradually reduced. Women begin to enter puberty at the age of 14, when the ovaries mature and begin to cycle ovulation and menstruation, fertility, fertility time generally lasts about 30 years, 25 to 35 years old is the most vigorous period of fertility. According to the survey, the relevant departments in China on obstetric physiology, eugenics and population control of the three aspects of the study proposed: the most suitable age for women to give birth is between 25 to 29 years old. Between this age, women are more fertile, the contraction of the uterus is very good, and there is less chance of difficult delivery. If the maternal age is too young (such as 20 years old), it is easy to combine gestational toxicity, preterm delivery, and also to obstructed labor due to incomplete pelvic development; if the maternal age is too old, especially over 35 years old, the possibility of oocyte malformation increases, and other chromosomal abnormalities and physical and intellectual congenital deficiencies often occur. For the male partner, the age of childbirth is related to the quality of the baby. Generally men are energetic and strong at the age of 25 to 35 and have higher quality sperm. Increasing paternal age also complicates certain chromosomal disorders. Neonatal mortality increases with the age of the father, and the incidence of malformations in children increases when the father is older than 40 years. Thus, births to men of advanced age are harmful to eugenics. The optimal age for childbirth is generally 25 to 35 years for men and 25 to 29 years for women.