If a child has a startle reaction, it should be considered to be caused by a physiological cause of startle. Generally, a three-month-old child’s ability to accept things is limited, so there will be a fright. It is advisable to let the child sleep on the mother’s body to get a sense of security and relieve the startle reaction. If it is not relieved, it should be considered as a result of vitamin D deficiency, you can go to the hospital for vitamin D measurement to check whether the vitamin D deficiency, and then give symptomatic medication, the symptoms should be further relieved.