There are many reasons why infants cannot raise their heads at 3 months, not necessarily due to intellectual developmental problems, but mainly due to physiological and pathological factors. Normal infants usually raise their heads around 2 months, and can raise their heads more stably at 3 months, but due to differences in individual growth and development, some of the infants with relatively slow growth and development will raise their heads later. Pathologic factors may be as follows: 1. Rickets: Infants with vitamin D deficiency cause rickets. The motor function of infants suffering from rickets, will be affected, and may appear 3 months unable to raise their heads. 2. Brain dysplasia: when infants have brain dysplasia, their motor function is more backward compared to infants of the same age, and they may not be able to raise their heads for 3 months. Parents are advised to take their babies to regular hospitals for comprehensive and systematic examination.