Why would mom be microwaving them?  If they have milk in, it's a
definite no-no.  Even lowly formula shouldn't be microwaved to heat,
even more so breast milk.
Is she trying to "sterilize" and reuse them.  Again, reuse wouldn't
be a good idea.
I think these are more concern than leaching chemicals into the
milk.  This would also be a concern, but IMHO there is no good
reason to do it in the first place.
Winnie

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