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Normal Childhood Growth

By Robert Lamberts, M.D.

The majority of pediatric medicine is done hoping that nothing happens. We see children on a regular basis as they grow up and really are only there to pick up things that are out of the norm. If all goes well, we are superfluous – the child would have done just as well if we had not been there. I sometimes tell patients that they want to be “boring” patients – if they are “interesting” to me, then there is something to worry about. What I offer my patients is a trained eye that looks at various aspects of growth and development and looks for anything that falls outside of the norm. The earlier we can pick this up the better the chance of successful intervention. The purpose of the next few articles is to discuss the various aspects of growth and development we watch through the childhood years.

As a pediatrician my task is done when a child grows from infant size to adult size. That doesn’t seem hard! Well, we make it more complicated than it sounds. You may have noted that we seem to be obsessed with graphing things, spending part of every well child visit looking at growth curves. The important growth parameters we follow are:

  • Length
  • Weight
  • Head Circumference

When I see a child for the well-child visits, I put these measurements on a standard “growth curve.” A growth curve is a set of standard heights and weights at every age. The child is plotted in these three categories against “normal” children at the same age. I will then inform the parents that their child (“Little Bubba” in these parts) is in the “90th percentile” (or something like that). This is no better or worse than if the child were in the 50th or 5th percentile. We look far more at the rate of growth (or “growth velocity) than we do the size of the child at any given time. I worry less about a child that stays in the 5th percentile throughout the first year of life than I do a child that starts in the 90th percentile at 2 months and is down to the 25th percentile at 6 months. The latter child is growing at a much slower rate than the former. Likewise, if a child’s head size is going up rapidly, we may suspect hydrocephalus (a build up of fluid on the brain). If Hydrocephalus is discovered early it can be easily treated, but if it is missed, the consequence can be devastating.

Some things that can effect a child’s growth include:

  • Poor nutrition – this effects weight first, but eventually height and head size are also effected. Sometimes this happens when a child is neglected, but sometimes there is a problem with breastfeeding or with absorption of food.
  • Metabolic problems – some children have kidneys that don’t get rid of acidic substances correctly (called a Renal Tubular Acidosis). The first hint that this exists is a child not growing properly in terms of weight. It is easilly treated and should be caught as early as possible.
  • Hormonal problems – Typically thyroid problems are picked up on newborn screening (called “PKU test” where I live). Sometimes, however, this may not get picked up on the newborn test and shows up later. Low thyroid in a child does not cause weight gain as it does in adults, it causes “failure to thrive,” or poor weight gain.
  • In older children, growth hormone deficiency is picked up when a child shows poor growth velocity over a sustained period of time.
  • Children with heart, lung, or genetic conditions can have poor weight and/or height gain compared to normal children.

It should be noted that most children don’t study the growth curve to make sure they comply properly. Every child has his/her unique growth pattern which may or may not follow the curve exactly. As I have been looking at growth curves for many years, it has gotten easier to tell what a normal variant looks like versus a significant problem. Don’t get too worried if your child changes percentiles from one visit to the next – we usually monitor it over a fairly long period of time (unless the change is dramatic).

It is also common to see kids in more affluent America to be on the large side (I see far more kids in the 95th percentile than I do the 5th). Sometimes a well-meaning health department employee will scold a mother when her 6 month old child is in the 90th percentile, saying that the child is “gaining too much weight.” Often these children have always been in the 90th percentile, and their height and head circumference are also in that percentile. I tell parents that unless they are feeding the child cheesburgers, there is nothing worry about. What are the parents supposed to do, suppliment with Slim-Fast? Infants in the 95th children are not at real high risk to develop obesity as adults. The biggest risk factors for adult obesity include hours spent in front of the TV, exercise (or lack of it), genetics, and healthiness of the diet as they get older. If a child is in the 95th percentile as a 5-year old, however, I do think a discussion with parents about diet and exercise is appropriate.

So do tall infants make tall adults? No, the best predictor of a child’s eventual height when he/she grows up is not the height as an infant, or double the height at age 2. The best predictor is called the “Mid-Parental Height.” This is where you take the height of the Mother and average it with the Father’s height minus 5 inches (for a girl), or take Mom’s height plus 5 and average it with Dad’s height (for boys). Obviously, this is a rough guess, as it would imply that all children of the same sex from the same parents will be the exact same height. But it is the best we have, so don’t make plans for the NBA draft yet if you have a tall infant. The Cheesburger usually does not fall far from the tree.

In my next article I will discuss normal childhood development.

Updated: June 30, 2013 — 8:08 am

2 Comments

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  1. I was searching for information on head cicumference growth in infants as my daughter’s measurements are a concern to me. My pediatrician won’t take time to explain them to me stating simply that they are “fine,” but I was hoping you could give me your opinion– I’ve been lying awake at night worried about her rate of h.c. growth.

    She was born with an h.c. at the 33 percentile with height at 72% and weight at 78%. At 3 weeks her h.c. was 46% and weight was 63% (no height avail.) At 2 months: h.c. was 52%, height at 68% and weight at 77%. At 4 months: h.c. was 67%, height at 79% and weight at 72%. At 7 months: h.c. was 68%, height at 60% and weight at 62%.

    My daughter is developmentally on target in all areas, but I am concerned about autism as I’ve seen studies about a connection with rapid head growth. Would you consider her growth to be abnormally rapid? By the way, my daughter was born “sunny side up,” with what looked like significant head molding, so could that have affected/lowered her birth measurement by a good amount? Would that explain the jump from the 33% to the 46% within three weeks?

    If anyone can help me to understand if her numbers are within a normal range, I would truly appreciate it. Thank you so much.

  2. Dr. Lamberts’ response to Jen’s comment:

    While there is no way to be certain of the fact, I agree with her pediatrician. I actually was unaware that there was any connection at all between head size and autism. When we look at increasing head size, we mainly look for non-communicated hydrocephalus – where the child develops a large head due to increased pressure in the fluid that surrounds the brain. This is, by the way, not associated with autism or with developmental delays.

    The change in percentiles are best explained by two possible explanations:

    1. The measurement is quite imprecise and most pediatric offices relegate the job to medical assistants. Just a quarter inch can cause a discrepancy for larger than the 13% mentioned.
    2. Growth curves are average growth patterns, but do not represent actual growth. Most children do not follow a curve in all categories. No child is absolutely average. You will commonly see children go up and down percentiles through their childhood. To see a 13% increase is not alarming by any means. It is common. If this should continue and accelerate to a higher rate of increase, then I would become concerned. Even then, however, I probably order about 3-4 head CT’s per year on kids for abnormal growth rates and have yet to have this be anything that that child’s peculiar pattern of growth.

    The thing pediatricians are most concerned about is development. That is by far the thing most indicative of autism or other significant problems. Most of my autistic patients began to start showing signs of developmental delay around 6-8 months of age. As long as development continues to be normal, the concern of autism should only be mild.

    Visit Dr. Lamberts’ blog here

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