The only study that I was able to find online was done on macaque, it proves that there is no effect on infants and only insignificant quantity goes into the maternal milk.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1087653/
The following is a paper from doctors in Francel. It said you can breastfeed whilst your are on Tenofovir because "Tenofovir is not absorbed in the breast milk". However, I have googled and cannot find any reference to this claim. All the best to you and your baby.
Clin Res Hepatol Gastroenterol.
2011 Jun 7. [Epub ahead of print]
Hepatitis B virus infection and pregnancy.
Pol S, Corouge M, Fontaine H.
Source
Inserm U-1016, unité d'hépatologie, université Paris Descartes, AP-HP, hôpital
Cochin, 27, rue du Faubourg-Saint-Jacques, 75014 Paris, France.
Abstract
Pregnancy only mildly affects that natural progression of
acute and chronic infection by the hepatitis B virus (HBV) but it does
bring to light three important questions. Mother to child (vertical)
transmission risk is best prevented by mandatory HBs antigen testing in all
pregnant women in their second trimester and by systemic serovaccination of
newborns of infected mothers. In mothers with high viral load, vertical
infection in utero could be prevented by lamivudine, telbivudine or
tenofovir treatment. Invasive obstetric or gynecological procedures (such
as amniocentesis, forceps, etc.) do not seem to increase the risk of
vertical infection. Breastfeeding is not contraindicated in maternal HBV
infection after serovaccination of the newborn. This holds true for mothers
on active treatment with tenofovir which is not absorbed into breast milk.
When it comes to managing active antiviral treatment, in absence of
virosuppression with lamivudine, tenofovir remains a logical step-up
treatment; in absence of virosuppression with adefovir, tenofovir also
remains a logical step-up choice as do tenofovir/emtricitabine combinations
or lamivudine in absence of preexisting resistance which may have been
induced during combination treatment of adefovir and lamivudine. In cases
of effective virosuppression with treatment by analogues, lamivudine should
be continued and entecavir should eventually be replaced by lamivudine,
telbivudine or tenofovir; adefovir should be replaced by tenofovir or
lamivudine in absence of resistance (which would require tenofovir therapy)
or adefovir which would restrict lamivudine therapy.
Yes,you can breastfeed.One of our members did and the baby is fine.Check enolia's posts about breastfeeding.