There will be seven study visits for women at study entry (Day 0), Day 2, between Days 5 and 7, at Weeks 6 and 12, and at Months 6 and 12 postpartum. Medical history, a short physical exam, and blood collection will occur at all visits. In Cohorts 1, 3, and 4, blood collection for PK studies will occur prior to receiving TDF and seven times post-dose.