Dear Michelle,

Graves disease is due to a thyroid stimulating antibody circulating in the
mother's blood.  Most treatments given to the mother do not remove this
antibody but suppress thyroid function.  This antibody can cross the
placenta in significant quantities and result in neonatal Graves disease
(neonatal thyrotoxicosis).  If the infant is affected, symptoms include poor
weight gain, tachycardia, tachypnoea, diarrhoea, and (if severe) cardiac
failure.  The infant may have a thyroid swelling (goitre).  The condition is
usually easy to treat but is rare, requiring the expertise of a pediatrician
with experience of its treatment.

The infants of mothers who have had Graves disease in pregnancy, whether
treated or not, or who have been treated in the past for Graves disease
(with thyroidectomy or radiotherapy) need to be carefully assessed if any
problems arise.  Breast-feeding is not contraindicated.

I hope that this helps.

Khalid Aziz
Memorial University of Newfoundland