Causes of chest depression in newborns mainly include funnel chest, normal physiological phenomena, as follows: 1, funnel chest: if the newborn has vitamin D deficiency rickets, it will lead to funnel chest, which is very common. Newborn growth and development is very rapid, if you do not pay attention to timely supplementation of vitamin D or usually sun exposure is very low, it will lead to a lack of vitamin D in its body, causing a significant decline in intestinal calcium absorption, calcium absorption, synthesis of the reduction will cause bone calcification is incomplete, resulting in chest depression; 2, normal physiological phenomena: newborns are relatively young, intercostal muscles are less mature, there may be with the respiratory This situation will gradually improve with age.