When we talk about cross-nursing, we should ask what the alternative is.
If a mother can't nurse for some reason, I think cross-nursing is a better
option than feeding donor or banked milk, since it satisfies the baby's need
to suckle, and allows the nurser's breast to produce a specific immune
response when inoculated by the baby.  Obviously, the mother needs to be
confident of the health of the nurser, but I don't see this as invalidating
it as
a resource.

Christine Gauthier wrote:
> I always wondered what really is
>happening when a mother nurses non-twins. Does both babies get what they
>need from the mom? Which baby controls the milk content?

Milk content is controlled by time since the last delivery.  If the nurser has
been producing milk for months, her milk will be appropriate for an older child.
For a neonate, this would not be optimal, but for a child more than a month
old, it would make little difference.  (The composition vs: time graphs in
Riordan & Auerbach show composition essentially leveled off after 30 days.)

Jonathan