Newborns have a heavier head and lighter lower body. Their spine and cervical curvature have not yet formed, and their muscles are not fully developed.
The lumbar spine cannot support the weight of the upper body, and the cervical spine cannot support the weight of the head, so newborns should not be held upright.
Avoid shaking the baby’s head vigorously. When holding the baby, always support their head and neck with your hand.