Infants will usually sit still at 6 months of age, but some infants may be too obese or wear more clothes, and the sitting time may be delayed until about 7 months of age. Since most of the infants in the first 6 months of life on the main sit and stand, but a small number of infants may be too obese or winter wear more clothes, may lead to sit and stand time delayed situation, if there is no other accompanying symptoms, this delay of half a month to a month of time is a normal phenomenon. If the infant has a lack of vitamin D may cause rickets, resulting in the emergence of infant motor development retardation, can not independently sit and stand, but also accompanied by excessive sweating, night terrors and other situations, parents need to take the baby to the hospital in time for relevant examinations, to determine the lack of timely supplementation can be.