This is strictly anecdotal, I don't know of any studies.
My oldest daughter was born with spinal abnormalities and it was recommended
to me that I take 4 mg of folic acid in the three months before conceiving
and the first trimester of subsequent pregnancies.  I did this and continued
to nurse her through my next pregnancy (and well beyond), no problems and a
healthy newborn.
I'm 25 weeks into the same routine.  My son is still nursing with no problems.
Of course, my daughter's only 4 1/2 and my son is only 2 so I can't say
anything about long term effects.
Sandy Rusby Bell
Burlington, Ontario

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