Dear Catherine:

My references are at work, so I will try to describe as best I can what I
have come to understand. (If anyone understands this more than me, please
explain it to me better!!)  I will provide the references when I uncover them
(I used to think piles were hemorrhoids, now I know they are large stacks of
"to read" articles stashed all around the places I live and work!)

Ketones are by-products of fat metabolism (when fat burning takes place as
the nearly exclusive energy source--remember the Dr. Adkins Diet in the
1970s?).  Ketones are normally taken care of by the body when the rate of
production is low.  Excess ketone production (which often takes place in
diabetes) can lead to acidosis and even death.

In late pregnancy, the hormonal picture of the mother is altered so that she
is insulin resistant and preferentially burns fat to free up glucose, the
preferred fuel for the baby.  This is the time of rapid brain development
(for the baby, that is, the mother's seems to go into remission...). When
ketones are high enough to be spilled into the mother's urine, it is a
definite signal to take action (get the mother to eat at more frequent
intervals.).  The time span between spilling ketones and the last feeding is
individual.  I find the most obese women need to eat the most frequently (but
not soda-pop and chips or desserts).  I f diagnosed with gestational
diabetes, these large women cannot maintain their high caloric intake (ever
try to fit 2800 cal of complex carbohydrate, protein and fat into a pregnant
woman?) and, in my clinical experience lose some weight.  Most of the
information regarding ketones and brain development is directed toward
gestationally diabetic mothers.  Our clinic tests all pregnant mothers' urine
for ketones on routine OB visits, but I'm not sure what they do when they
find it besides write it on the chart. (I guess I'd better inquire).
 Acidosis is not the most favorable environment for brain growth (ketones can
and do cross the placenta).

Hope this helps a little....

Martha Grodrian Brower, RD, LD, IBCLC
Nutrition Trivia de jour