The worry about goiter (enlarged thyroid) in pregnant women is that their
iodine deficiency will lead to mental retardation in the child, known as
"endemic cretinism."  However, the mother must be *very* iodine deficient in
order for the child to be affected.  In two of the villages I did research
in in Mali, almost every adult woman had a goiter, many of the men did, and
even many of the children (very unusual to see goiters in children), but
there weren't any children with endemic cretinism.  And some of those
goiters were the size of basketballs (I kid you not).  So the goiter itself
is probably not a worry, assuming mother is now getting enough iodine in her
diet.  It will take a long time for the goiter to regress.  I don't know
anything about the drug you mentioned though.  Maybe Dr. Hall is reading?