I am an LLL Leader and IBCLC, I also have a daughter with MG.  I can tell
you a little about it.There are actually 3 types of MG.  The first and most
common is an auto-immune type that is caused by antibodies acting against
acetylcholine receptor sites prohbiting the nerve impulse from being uptaken
by the muscle.  As a result you get muscle weakness. This may be progressive
and degenerative. The second type in called congenital myasthenia and is
seen in newborns and may precipitate a crisis immediately after delivery.
This is caused when a mothers antibodies accumulate in the baby causing his
muscles (swallowing and breathing are the problems) to not work. Generally,
the baby does not have continuing problems with MG after the crisis.  The
third type is also called congenital and is a deformity of the muscle end
plates, we do not think it is progressive nor degenerative, but it too
interferes with acetylcholine uptake.

For breastfeeding, there are no contraindications with myasthenia gravis.
Medication use may be a big issue depending on the drugs, mestinon or
pyrostigmadine is not contraindicated in BF. There is need to help the
mother find comfrotable positions for nursing- lying down seems to work the
best, there also seems to be a need to change position frequently.  If the
baby has an MG crisis, BF will probably be contraindicated until s/he can
take anything by mouth and is off respirator etc. If the mother has the
autoimmune type she may be on some major steroids or immunosuppressants-
these may be contra-indicated at the high doses used. Immuran is being used
a lot lately. Plasmaphoresis is a technique that filters a mothers blood and
returns it to her with reduced antibodies.  This procedure is not
contraindicated during breastfeeding.

In terms of encouraging a mother with MG to breastfeed, we need to remember
that this may be the one thing she can do for her baby.  We also need to
remember that contrary to popular belief- BF is not draining, would not
worsen the MG by itself, and may allow a woman to rest and recharge and
energize her. I like to make the analogy for my daughter of a cordless
phone- when the battery is dead-you can't talk any more- return it tyoo its
cradle for charging and it works again.  For someone with MG resting or
lying down may work well to recharge them. Another consideration for
encouraging BF though is the mounting evidense that bf protects against
autoimmune illness and may help protect the baby from MG- no studies, just
my observation based on studies of other autoimmune diseases- MS and diabetes.