Lisa - see your dilemma, it is vexing!  There seems to be a lot of
conflicting info about this drug and breastfeeding, most sources recommend
using a single 2g dose and pumping and dumping for 12 hours:-
  B/F and Human Lactation p 141
  JHL June l99l, p 86
  JHL Mar  l993, p 45 (four different studies, different results ..)
  B/F Management in Australia, p 130
  Drugs in B/F and Lactation p 431

Some of our doctors do it differently here.  One gynae routinely prescribes
metronidazole following all his Caesars, the babies are all breastfed.  One
of my clients was prescribed 200mg 3 times daily and her paed confirmed that
breastfeeding need not be interrrupted.  I have also checked this several
times with our City Health Department Clinics whose Sisters confirm that
they will prescribe 400mg 3 times daily for 7 days as necessary WITHOUT
interrupting breastfeeding.  They advise that the breastmilk may taste bitter.

B/F Management in Australia (yes, again!) p 150 states, under the Heading
"If systemic therapy is needed then:  According to information currently
available, is the drug regarded as safe in the neonatal period?  Is the drug
routinely used to treat newborn infants who themselves have a medical
condition requiring drug treatment?  For example, metronidazole (Flagyl) is
listed in many tables and charts as being contraindicated while
breastfeeding, or to be used with caution.  In clinical practice the drug is
used extensively for mothers post-partum, especially following abdominal
surgery.  Its apparent safety is emphasized by the fact that metronidazole
is commonly used in special care nurseries to treat necrotizing
enterocolitis in the neonatal period and infancy.  The initial
recommendations and cautions were based on the early animal studies which
raised concerns about the long-term effects of the drug because of possible
mutagenic and rumorigenic potential.  Any concerns should be balanced by
information from the manufactgurer of the drug that the animals in the study
were given 3,000 times the corresponding adult human dosage and the tumours
produced were benign.  Additionally, the drug now has an excellent
twenty-five year safety record and recentt articles have recommended that up
to 400mg three times a day can be considered as a safe dose for nursing
mothers..." .. However to minimize effects etc etc this info is followed by
AAP recommendation ..

Is she able to obtain the opinion of another paed more supportive of b/fing?
Hope your young mum is able to work this out.

Pamela, Zim