Laurie:  Is it possible to get more information on this case?  There are
some confusing statements in your posting.  For example, you state that
the mother's prenatal RPR was positive, but that follow-up blood tests
were negative for syphilis.  There is a fairly common false positive rate
with RPR's (i.e. the test is positive but the person does not have
syphilis).  The confirmatory tests are treponemal tests such as FTA-ABS
or MHA-TP.  If they were negative, then the mother does not have
syphilis.
However, postpartum this mother has a positive RPR.  If the original test
had been false-positive, then she should have the treponemal confirmatory
tests done.  Since she is being treated with Penicillin, I must assume
that these tests confirmed syphilis.
If the mother had syphilis, you are correct that the baby was already
exposed.  Syphilis has four stages: primary infection, with a mucosal
lesion which occurs 9 to 90 days after contracting the disease, and is
infectious until it heals in 4-6 weeks; secondary syphilis, usually
occurring within weeks or months of the primary, has many symptoms
including rashes, fever, weight loss and headache; latent stage, with no
symptoms but still an infectious potential, lasting several years; late
or tertiary syphilis, which is considered non-infectious.
I will look for references if available, but if both mom and babe are
treated simultaneously, there appears to be no reason to wean.  The usual
treatment is benzathine penicillin injections weekly for three weeks.
Hope this helps.  Alicia.  [log in to unmask]