Dear all:

This is a topic that periodically crops up and about which Kathy Dettwyler
used to respond frequently.  Since she has not been participating on
Lactnet for a while, I thought I'd make some comments now.

My background is in nutritional epidemiology and one of my professors was
actually a physical anthropologist, well versed in anthropometry.  Having
worked in developing countries, growth monitoring was a huge part of
nutrition interventions.  I also worked with some of the folks at CDC who
developed the new growth charts - so I know how tricky and onerous the
statistics are for developing growth charts.  It is not by any means and
easy job to develop these.

So, lets go over a few items that have been discussed.

1) Weights and lengths were lower in the past.  Much of the lower weights
and lengths for infants and chilren under five several generations ago were
due to malnutrition, as are the differences seen between developing
countries and developed countries. The genetic differences between
populations living in different countries is also actually quite minimal.
Both of these observations are well-documented in the scientific
literature.  When looking at "healthy" well-nourished children in the past
and in various different countries, one sees surprisingly little difference
in growth rates.  Even well-nourished pygmy children grow at about the same
rates as other populations during the 0-5 year old age range.  About the
only population where the literature suggests that there may be some slight
differences are the South East Asian populations and that difference is
minimal - about 1 cm.  (Reynaldo Martorell has done a lot of work on this
issue if you care to do a literature search).  What we are seeing in the
most recent period is a rapid increase in UNHEALTHY growth - i.e. obesity

I want to make it very clear that while genetics does not play much of a
role in differences between populations, it may very well play a strong
role in individual families.  So those of you who have families that tend
to be large and those of you who have families that tend to be small - it
is most likely genetics.

2) The old charts are only based on bottle fed infants. This is actually
false.  The old charts were based on a population of infants who were fed
by mixed feeding methods.  What this means in terms of the growth charts is
that the SPREAD of growth may possibly be wider than it should be, because
of the "unhealthy" extra weight gained by formula fed infants during the 4-
6 month period.

3) The old charts are not useful because bottle fed children are included.
This again, is not true. The charts have been used in many nutrition
programs in developing countries with success.  The charts are only useful
if you look at the tragetory of growth, not the percentiles.  One looks for
sharp dips in growth.  AND since it is well known that the weight gain
of "healthy" breastfed infants tends to be lower in the 4-6 month period -
a slight downshift in the percentiles is expected.  Slight deviations are
not of concern.  A drop of 2 z-scores, which I have never heard used in
pediatricians offices or on LACTNET, but are widely used in developing
countries, is what usually triggers looking at a child's situation more
closely.

4) The new growth charts on breastfed infants will solve all our problems.
This is where I have to pipe up with what Kathy Dettwyler has mentioned
before on LACTNET.  The new charts are based on US moms - who do not often
practice breastfeeding the way that it is practiced in developing
countries.  We schedule, we train infants to sleep through the night, we
have them sleeping in cribs.  This may very well play a role in reducing
the upper end of the curves on the breastfed charts.  Furthermore, these
are the women who succeeded.  In our US society, there is pressure to
supplement slow gaining infants with formula.  Some of these infants
actually may have been exhibiting normal healthy growth for their
physiology.  These infants would have been eliminated from these charts.
So - this may have reduced the lower end of the curves on the breastfed
charts.

Finally, none of this is relevant anyway if one simply monitors the growth
tradgetory AND the infants health and behavior.  Growth alone is only one
piece of the pictures.

Susan E. Burger, MHS, PhD, IBCLC

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