If a newborn loves to laugh, mainly consider pathological and physiological causes, as follows: 1, pathological condition, if the newborn suffers from congenital stupidity, also known as trisomy 21, intelligence is often significantly reduced, developmental delays, some will also appear congenital heart disease and other malformations, the reason why newborns love to laugh, often due to mental retardation caused. For this situation, there is no particularly effective way; 2, unconscious love to laugh, belongs to the physiological love to laugh, because there are children will appear easy to laugh, growth and development is normal, mental state is also better, eyes are also more lively, belong to the normal physiological response, parents do not need to worry too much.