Newborn baby old straining, usually caused by the following two reasons: 1, the growth rate is too fast: the first three months after birth growth rate of newborns is very fast, whether height and weight, or other aspects, the growth rate is very fast, the baby for such rapid development, may be momentarily uncomfortable, which leads to physical discomfort, there will be stretching, old straining, but also stretching arms, legs and other phenomena, old straining may be Want to relieve the discomfort caused by rapid growth. 2, defecation effort: newborn children usually do not occur constipation, when the baby has the intention to stool, the nerves will issue instructions to increase the pressure in the chest cavity, so that the diaphragm moves down, while the abdominal muscles contract to allow the abdominal pressure to rise. But because the neonatal nervous system is not well developed, the pelvic floor muscles, which should be relaxed, become tense, which can lead to the baby’s defecation effort and old effort. As the child grows and develops, this phenomenon will disappear slowly.