This is a situation in which it would be very useful for the mother to
take calcium supplements and vitamin D during her pregnancy and after
the baby is born.  The situation of an anorexic (or former one) may be
quite different than someone else.  She may have had a tremendous lack
of accumulation of calcium and phosphorus during her teen years when
growth is often rapid.  The rebound for bone density that you mentioned
was described in presumably normal women who had no previous history
such as this woman.

It might be of interest that in a nutrition clinic where I work, a pilot
study showed that women who had anorexia and were coming to the clinic
for that reason had rarely been breastfed themselves.

The value for the child of breastfeeding is immeasurable.  Why assume
the worst?  Go for the breastfeeding, take the vitamin D (or at least
get into the sun) and the extra calcium and follow bone densities.

Jack Newman, MD, FRCPC