The weight and size of a baby at birth usually varies according to some specific aspects, what if it should be clear, is that according to the size that is born, it is not classified as being small or tall, since this depends on the family genetics and the development that the child has during pregnancy.
Babies when they are born do not have all the same weight and height, since this varies according to some conditions of the baby during pregnancy, or for other reasons that will be explained below.

The feeding that the mother had during her pregnancy is vital, if the feeding was not correct, the child may have presented problems in their growth and in gaining weight, the feeding is very important since the nutrients that the child receives medium of his mother, is what makes an optimal development, cerebral and physical.
If difficulties or complications arise during pregnancy, they can generate changes in the size of the baby.
These complications can be problems of tension or an infection that the mother presented, stress or depression, this affects the growth and the weight of the child definitely.

Although a size or exact weight of a baby at birth is very relative, an average size is used in which the newborn should be the reference point that determines whether the baby is underweight or underweight
For example, a baby when it is born can measure between 46 and 53.3 cm and weigh between 2,500 to 4300 kg, in case of being a child and if it is a girl, it can measure between 45.5 and 53 cm, weighing between 2,400 and 4200 kg, this average allows to relate if the baby presented a variation of weight either low or increasing.
When a baby is born small, it is possible that it presents difficulties to eat, for this reason it is better to follow the indications of the pediatrician according to the cause. It is necessary to follow the doctor's recommendations to the letter and be in control for as long as necessary.
According to doctors babies must increase their weight in the first months of life between 700 and 900 grams, when they reach the third month only increase from 500 to 600 grams, when they reach the sixth to 9 months, the average increase is 350 at 400 grams, between 10 to 11 months increases 250 or 300 grams per month.