Infant limb weakness may be related to fever, gene chromosome abnormality, and spinal cord damage. 1. Fever: When the baby’s body temperature rises, the body’s metabolism slows down, not only the gastrointestinal function decreases, but also muscle tone, mental lethargy, limb weakness and other manifestations. Parents should give the child a timely temperature measurement. 2. Genetic chromosome abnormalities: congenital hypothyroidism or 21-trisomy syndrome and other genetic chromosome abnormalities in children, can appear mental retardation, decreased muscle tone, etc., manifested as limbs flaccid, need to go to the hospital to perform the relevant tests to confirm the diagnosis. 3. Damage to the spinal cord: when the baby’s spinal cord is hit hard or there are spinal cord tumors, there will be limp limbs, intellectual development is generally not affected. Infant limb weakness may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.