Pediatrics Today

How Does Your Baby Grow?

Infants spend a lot of time growing during their first year of life. Normal growth depends on three main things: genetics, nutrition and hormones. Each time your infant visits the doctor for a well-visit checkup, she'll be weighed, have her height measured and have her head circumference calculated, which will all then be compared against a standard growth chart. This is to help establish a growth pattern, and also allows your pediatrician to detect any deviations from it which signal a problem, such as a nutritional deficiency.

Weighing In
Typically, a newborn loses 10 percent of his body weight within the first week. But by the time he's two weeks old, he should regain or even exceed his birthweight, gaining about one ounce per day during the first three months. Between 3 and 6 months, this slows down to about 1 1/4 pounds per months, and then a 1/2 ounce per day between 6 and 12 months. With this rate of growth, your infant should double his birth weight by 4 to 5 months and triple it by the time he's 1 year old.

Reaching New Heights
Most newborns average length is 20 inches at birth. An infant grows in length at a rate of 3.5 cm per month in the first 3 months; 2 cm per month between 3 and 6 months; and 1.2 to 1.5 cm per month between 6 months and 1 year. The infant's length averages 75 cm at 1 year of age.

The Role Genetics Play
Changes in the growth rate are not so unusual during the first two years of life, and can depend on the size of the parents (i.e., large infants born to small parents tend to slow their growth, whereas small infants born to large parents tend to accelerate it during the first two years of life.) In such cases, the determinant of small size is genetic and should not raise concerns. In other words, the apple doesn't fall far from the tree.

Conditions that Hinder Growth
Nutrition is the most important factor that influences growth. Conditions that might prohibit an infant from getting proper nutrition include:

Structural malformations of the face and mouth, including cleft lip and palate.
Neurologic disorders leading to the inability to suck and swallow normally.
Gastrointestinal diseases manifesting with vomiting and/or diarrhea.
Psychosocial problems as in child neglect or disturbed mother-infant relationship.
Cardiac or respiratory disease where exhaustion and labored breathing may lead to inadequate dietary intake.

This is why it's important to pay special attention to symptoms suggesting illness (including vomiting, diarrhea, feeding difficulties and respiratory distress), as well as your baby's eating patterns and general behavior.

In infancy, many children who fail to thrive show developmental delays and abnormalities of posture. This is why malnutrition during the critical period of brain growth should be identified promptly and treated vigorously to minimize central nervous system problems.