Correcting Pre-Exposure Prophylaxis (PrEP) Dosing and Adherence Benchmarks in Pregnancy to Optimize HIV Prevention (PrEP-P): A Randomized Comparative Pharmacokinetic Trial

Study participants will be randomized to one of two parallel study arms, involving dosing of tenofovir disoproxil sodium/emtricitabine (TDF/FTC). The investigators will be recruiting and enrolling in the late 1st (preferred) and 2nd trimesters of pregnancy to capture the changes in kidney function and blood flow through the kidneys that appear to start in the late 1st trimester and are most significant in the 2nd and 3rd trimesters of pregnancy. Given the unknown time frame for the return to pre-pregnancy physiologic state and the increased risk of HIV acquisition postpartum, participants will be continued on study dose PrEP until after participants' 1-3 week postpartum visit, after which all participants will be dispensed standard dose PrEP. A 6-12 week postpartum study visit will also be performed to evaluate the timing of return to non-pregnant plasma drug levels during the postpartum period.

PK Sampling. Primary PK data will be derived from up to 7 study visits with PK sampling, including two PK visits in each trimester and postpartum. All PK visits sample blood before an observed PrEP dose. .

Safety Sampling. Maternal safety assessments will continue until 6 months postpartum. Fetal evaluation includes non-invasive limited ultrasound (US) and biophysical profiles (BPP) at study visits and 2nd and 3rd trimester interval growth US, and chart review of all before birth assessments. At birth, the investigators will obtain cord blood plasma to assess for mitochondrial function. Infant safety assessments will continue until 1 year of life. Infants will undergo swaddled Dual-energy X-ray absorptiometry (DXA) scans (without sedation) at 3-6, 24-28, and 50-54 weeks of age. The investigators will assess kidney function by blood sample at 3-6 weeks of life and repeated at 24-28 weeks.