An Endocrinologist Perspective
As a pediatric endocrinologist, I frequently evaluated growth. Most commonly, there was concern regarding short stature, too little, or too much weight gain. Little ones born prematurely or small for gestational age (SGA) also were referred.
Growth depends on numerous factors that include:
Birth history - prematurity, small for gestational age (SGA), hypoxia (low oxygen)
Family history and height of family members
Timing of puberty
Genetic conditions
Pituitary function, specifically growth hormone and thyroid hormone production
These factors can all affect the genetic potential of growth in a child. I will review normal growth expectations in this article.
First, understand that the size of a newborn and infant during the first year of life does NOT predict the size of the child or adult they will be.
An infant roughly doubles its birth weight by 4-5 months and triples it by 12 months.
They will quadruple their birth weight by 2-2 ½ years.
The length of an infant should increase by 50% at 12 months and double by 4 years.
An infant usually grows about 8-10 inches or 20-25 cm in the first year.
Once a newborn starts gaining weight (after the first 1-2 weeks), they will gain about ½ pound per week or a pound every 2-3 weeks during the first six months.
From 6-12 months, the rate of gain is ¼ -⅓ pound per week. Babies are actually on a slowing trend once they exit the womb!
Preterm and SGA infants can gain more rapidly or more slowly. These infants should be allowed up to 2 years to “catch up” in their growth and often will establish a growth curve parallel to and below the regular growth chart. There are separate growth charts for premature infants.
Toddlers often do not settle on the growth percentiles they will follow for the rest of childhood until age three. There can be fluctuations until this age.
Once a child reaches the age of three, they should grow 2-3 inches or 5-7 cm a year and gain 4-10 pounds (ideally 5-8 pounds) a year.
These parameters will keep them on the same percentile growth curve until puberty and the growth spurt.
A child being measured by her doctor
Pediatricians measure and plot the growth parameters at each well-child visit. Consistency with these visits is essential to detect abnormalities. If there is a concern regarding growth or weight gain, I encourage you to address this with your child’s doctor and not wait until the next well visit if that is months away. I was often frustrated when finding a chronic problem in a patient that I could have detected sooner had regular check-ups been kept. An earlier diagnosis can often improve the outcome.
Once puberty occurs, the linear growth (growth in height) accelerates to double or triple the pre-pubertal growth rate. This acceleration will often cause an increase in height percentiles. Puberty also increases muscle mass in males and body fat in females leading to an acceleration in weight gain and some increase in weight percentiles.
If the linear growth accelerates before puberty OR decelerates to cause an increase or decrease in percentiles, then further evaluation is indicated. There can be some measuring error; the first step is to remeasure! From age 3 until puberty, growth should be consistent and stay along the same curve in height and weight. Height and weight may be at different percentiles, but a child should be tracking consistently. Deviations from this can be a cause for concern.
A child whose weight is rising rapidly but whose height continues to track normally usually does not have an endocrine or hormonal problem. However, rapid weight gain does increase the risk for insulin resistance, metabolic syndrome, and type II diabetes. I could sometimes discern an endocrine issue or a chronic condition by evaluating the growth chart.
There are ways to predict adult height based on formulas, the growth chart, and bone age x-rays, but doubling a child’s height at age two is often within a couple of inches.
These are general guidelines for monitoring growth in your child. Should concerns arise, it is best to address these with your pediatrician, who can further guide you.
Next week, I will review puberty and the obesity link….stay tuned!