One of the most unique aspects of pediatrics is growth and development… and how these impact your evaluation. Even in the emergency department these must be considered. For instance, when determining if that 6 month old was able to crawl into the bathtub and get burned on his/her own it is good to know basic developmental milestones (we’ll discuss in the future). Additionally, having a working knowledge of basics about growth may prove to be useful to you when assess for complaints like vomiting (is this 4 month old who is 9 kgs failing to thrive or being overfeed?). Here are some gross growth estimates that I find helpful.
Failure to Thrive?
An infant with failure to thrive will first demonstrate poor weight gain.
With continued insult, there will be reduced height/length growth and then, finally, reduced head circumference growth.
After birth, infants will normally loose weight initially (particularly breastfed infants).
Infants should regain their birth weight by 2 weeks of life.
For the first 3 months, infants should gain ~30 grams a day (~1 oz / day).
By 6 months, they should have doubled their weight.
By 12 months, they should have tripled their weight.
By 24 months, they should have quadrupled their weight.
Other useful numbers:
At 1 year of age, your average child will be ~10kg.
At 3 years of age, your average child will be ~ 15kg.
At 6 years of age, your average child will be ~ 20kg.
Unfortunately, at least in the USA, our children are greater than average with respect to their weight; but, these are good starting points when you need to estimate weight in a pinch.