The mother is right.  She has been told the risks, and she wants to
continue breastfeeding.  No one has the right to tell her otherwise.
The question is, is there an increased risk?

Well, no one knows the cause of otosclerosis.  There are many
illnesses which get worse during pregnancy, and no one knows why, in
the majority of cases.  But pregnancy is not the same state as
lactating.  Indeed, if it is the estrogen levels which are supposed to
exacerbate the otosclerosis, the mother is better to continue
breastfeeding, as if I remember right (hormones always confused me),
estrogens tend to be lower during lactation than when not lactating.

Jack Newman, MD, FRCPC