The newborn baby wakes up very frequently in bed, consider the baby is jumping reflex. The cortical function of the brain of a newly born baby is not well developed, and when the external sound is transmitted from the ear nerve to the nerve center of the brain, the nerve impulses can simultaneously ripple to the nerve fibers controlled by the brain, causing the muscles of the limbs to tremble. Loud sounds, bright lights, vibrations or changes in body position can cause babies to jump. The startle reflex is the action of its own reaction, the baby shows the hands up and open, and quickly retracted, legs straight, and sometimes cry, hand movements and cries aggravate the degree of fright, and cry more fierce. Sometimes the sound and vibration are not too loud, but also when the distance is close, the startle reflex will generally disappear slowly at 3-5 months of age.