There is absolutely no reason for the mother not to breastfeed.  A
longitudinal study from Taiwan, where 15% of all women of child bearing
age are, or were, Hepatitis B positive, showed no difference in pickup
by the baby depending on the type of feeding.  The reference is:

Beasley RP, Stevens CE, Shiao IS, Meng HC.  Evidence against
breastfeeding as a mechanism for vertical transmission of heapatitis B.
Lancet 1975;2:740.

Note that this study was done before we immunized babies against
hepatitis.  Now that we give them immunoglobulin and immunize them,
there should be no concern at all.

Physicians who don't know anything about breastfeeding and advise
mothers not to breastfeed.  AARGH!

Jack Newman, MD, FRCPC