First month: 3.0-3.6 kg for boys and 2.9-3.5 kg for girls. After that, the weight increased by 30 ~ 40 grams every day, and after one month, the weight increased to 4 kilograms. The second month: the average weight of boys is 5.2kg, and that of girls is 4.8kg. During this month, the weight gain is about 900g (about 30g per day). The third month: subcutaneous fat developed and became stronger, and the weight was twice that of birth, with an average of 6 kg for boys and 5.5 kg for girls. About 28 grams a day. Babies will lose weight from the third day after birth. This is because newborns begin to excrete urine and meconium, and because of the action of skin and exhalation, they evaporate water and absorb less milk. Generally speaking, the baby's weight in this period will be about 10% less than that at birth. After they drink milk successfully, their weight will start to rise, and on the tenth day after birth, their weight will return to its original state (the same as when they were born). The weight and height of newborns are closely related to the nutritional intake of mothers during pregnancy.