The development time of infants may vary somewhat. Generally, infants can sit up fully when they are about seven months old, and it is recommended that babies be allowed to sit in a safety seat only after seven months. In the process of infant development, before seven months the infant’s bone development is not fully mature, the back muscles can not support the whole upper body well, at this time it is not recommended to let the baby sit alone or give the baby to sit in the safety seat, so as not to affect the growth of infants. After seven months of bone development and muscle development can support the upper body, can sit in the seat. Safety seats can be in the car, better fixed baby, protect the child’s safety, parents should choose the child’s height and weight of the safety seat, in order to be able to have the greatest help to the baby.