The weight of a full-term baby born in the range of 5-8 pounds is normal, if the weight is less than five pounds belongs to the low weight baby, more than eight pounds is a huge baby, affecting the birth weight of newborns are the following factors: 1, the age of first birth, the age of first birth in thirty years, the weight of the newborn is at its highest value. The younger or older the mother, the easier the baby’s weight is light. 2, pregnancy week, forty weeks is a whole pregnancy cycle, the fetal baby in thirty-five weeks began to grow rapidly, preterm babies are light weight is to miss the very rapid growth period, and more than forty-two weeks is an overdue pregnancy, is also not conducive to baby growth. 3, pregnancy conditions, the nutritional status of pregnant women, the degree of health, maternal hobbies will affect the baby’s weight at birth. 4, genetics, the baby’s weight also has a certain relationship with the parents’ weight and height.