Please excuse my not citing individual posters from this thread.  Just got
up after sleeping not long enough after night shift.

It seems logical if you think of lactation as a basic survival function,
that when mothers are leaner, they are less likely to get pregnant.
'Nature' protects the already born nursling's milk supply this way.

There are a lot of rough estimates of milk production, and depending on the
source, they may be simple repetitions of the volume of commercial
breastmilk substitutes needed to sustain growth, and thus misleadinly high.
It has been well demonstrated that less breastmilk is needed, since the
metabolic 'cost' to the child for digesting and burning the food is so much
lower.  In studies researchers have weighed children before and after feeds
for extended periods, and the painstaking level of detail is impressive.

Many years ago, so many that I only remember the very major findings and not
the author, I read an article in BIRTH in which it was shown that mothers of
twins had a milk production curve that looked more like dairy animals'
curves, with a much higher peak production around 3-4 months than mothers of
singletons.  The latter seemed to plateau around 3 months while the MOT
group had a production about double that (why are we not surprised to learn
this?).  Even if continuing exclusive BF, the baby's lowered metabolic and
growth rates over time make the same volume of milk continue to be
sufficient for growth in the latter part of the first 6 months.

From personal experience I can report that my ample energy stores with my
first pregnancy, were completely gone by 6 months post partum, even though
my exclusively BF child had only gained about half of what I had lost.  As
my weight approached pre-pregnant weight, my appetite increased
dramatically.  As long as I was lactating at all, I was hungrier than before
and could eat anything in any amount I wanted, with total impunity,
something I have longed for many times in the intervening years.  My
pre-pregnant BMI was in the low end of the normal range.  Alas, it has
migrated upward in recent years.  There is no reason whatsoever to think
that a woman whose pre-pregnant BMI was high, would have the same metabolic
features as mine while lactating.

One sad thing to realize is that if increasing BMI is related to less
success in BF, as some have reported, the very women who might benefit most
from BF's effects are the least likely to enjoy them - and their children
are more likely to be exposed to the health risks of short BF, such as
obesity.

I think the theory of prenatal hormonal imprinting may be able to shed light
on this topic - why some babies are born lean and have certain health risk
characterictics which are different from the health risks inherent in a high
birth weight with high BMI.

The article by Atul Singhal et al (incl. Alan Lucas) on 'Low nutrient intake
and early growth for later insulin resistance in adolescents born preterm'
(Lancet 2003;361:1089-97) is disturbing reading.  They interpret their
findings, and I quote from the authors' summary, thus:
"Our results suggest that relative undernutrition early in life in children
born preterm may have beneficial effects on insulin resistance."
We need to be aware that the final word on things like the use of calorie
and protein fortifiers with breastmilk in premature babies, is not in.  We
probably don't know everything there is to know about optimal growth
trajectories for individual children either.  We must base practice on the
best available knowledge, and welcome new knowledge as it appears.  I doubt
very much whether today's policies on fortifiers will be unchanged five
years from now, and I would guess that future policy will reflect a better
understanding of who really benefits from fortification and who might be
better off without it.

Rachel Myr
Kristiansand, Norway

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