After the baby is born, he does not have any ability to express his words, so any discomfort or uncomfortable situation, will choose to cry to express, so parents should learn to understand which aspects of the child may have a problem, resulting in the child is not able to sleep quietly. 1, the child does not adapt to the natural environment, if the night and day reversed, parents work during the day he sleeps, parents rest at night when the child gradually become already very awake, so at night it is easy to cry. 2, the baby’s nervous system has not yet developed, can not fully control, the function is relatively weak, if in the daytime stimulation then at night when sleeping, his brain is in a state of excitement will be easy to suddenly cry. 3, if the child has the influence of disease, will also be easy to cause sudden crying at night, such as long-term pain or cold and fever nasal congestion may lead to sudden crying. 4. If the mother has always taken care of the child, and suddenly the mother has something to do with the father or nanny, it will be easy for the child to cry suddenly because of the change in caregivers. Children are very interested in everything in the world when they are young, so if there is a sudden change or change, it is easy to irritate the child and make them cry at night, probably because they are hungry or have pooped and peed.