An alternative to oral Flagyl is Metro-gel, a metronidazole vaginal cream.
Although it works better for bacterial vaginosis than for trichomonas, it
would be a temporary measure that will probably have to be repeated from time
to time until the mother stops nursing.

Perhaps Dr. Hale can tell us if oral Flagyl is actually contraindicated in
nursing.  It is a drug that is used on small children for parasites.
V. Nichols Johnson, MD