Dear all:

If you look at the percentile curves for boys and girls, you will notice that there is a HUGE amount of overlap in growth.  One of the things about gender based comparisons that is often forgotten is the same thing that is often forgotten in ethnic based comparisons (race actually is a social, not a biological construct).  The OVERLAP among different groups is far less than the VARIABILITY within a group.  While there is some biology behind gender based differences, there is a huge amount of overlap.  This means that any female Olympic athlete would mop up the floor with an untrained male and even then you would find some female Olympians that could still mop up the floor with some of the male Olympians. 

So, spending some time on my New Year's Day procrastinating about a much larger task I'm going to undertake, I spent a little bit of time on the growth curves to demonstrate the problem with such generalizations on differences in growth.  I won't even comment on the intelligence testing and the problems with such studies.  If you want to read about that, I wrote an article many years ago in the American Journal of Clinical Lactation.  There are enough other studies on intelligence which is extremely hard to measure, that show a difference for girls as well that I'm convinced that formula feeding isn't harmful for girls as well in terms of their mental development. While it is fun to surmise if you are female that you are more resilient than your male counterparts, I would hardly think one study on a challenging topic is enough to really much such a conclusion at this point in time.

So, on to the reason why gender growth is not as important as looking at healthy growth for the individual child.

The difference at birth between the girl who is at the 3rd centile and a boy who is at the 3rd centile is 67 gm or 2.4 oz
The difference at birth between the girl who is at the 97th centile and a boy who is at the 97th centile is 234 gm or 8 oz

In comparison, the difference between the girl at the 3rd centile and the girl at the 97th centile is 1726 gm or 3 pounds 12.9 oz
And the difference between the boy at the 3rd percentile and the boy at the 97th centile is  1843 gm or 4 pounds 1 oz


Then moving on to the 60 day old.

The difference at birth between the girl who is at the 3rd centile and a boy who is at the 3rd centile is 378 gm or 13.3 oz
The difference at birth between the girl who is at the 97th centile and a boy who is at the 97th centile is 459 gm or 1 lb 0.2 oz

In comparison, the difference between the girl at the 3rd centile and the girl at the 97th centile is 2598 gm or 5 pounds 11.7 oz
And the difference between the boy at the 3rd percentile and the boy at the 97th centile is 2517 gm or 5 pounds 8 oz


Best regards, Susan Burger

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