Regarding the causes of delayed development of babies, there are several reasons: 1, abnormal hormone levels: for example, if there is a lack of hormones that can promote the growth and development of the body, babies will experience developmental delay, such as thyroxine, growth hormone, etc., which is a relatively common cause of growth and developmental delay. If the baby is relatively small, sexual development is not obvious, even if the lack of sex hormones, not necessarily manifested in childhood, growing up there may be certain symptoms appear; 2, the existence of disease in the body: for example, there are malnutrition, recurrent infections, tumors, and other factors that will cause chronic depletion of the body state, may also affect growth and development; 3, genetic aspects of the problem: for example, genetic mutation of the disease may cause growth retardation, this disorder may be in pregnancy, in the embryonic period may have been formed, after birth may be more obvious. In short, if the baby has growth retardation, it is recommended to go to a specialized hospital to find a pediatrician to make a comprehensive judgment and assessment, to find out the specific causes of the disease, before being able to target the cause of the treatment.