Detectable HIV RNA in late pregnancy associated with low tenofovir hair levels at time of delivery among women living with HIV in the United States.

OBJECTIVE We evaluated peripartum tenofovir (TFV) exposure via hair measures among women living with HIV (WLHIV) in the United States. DESIGN Observational cohort study METHODS:: Hair samples were collected at or shortly after childbirth among mothers enrolled in the Surveillance Monitoring for ART Toxicities Study of the Pediatric HIV/AIDS Cohort Study (PHACS) between 6/2014-7/2016. Among mothers receiving tenofovir-disoproxil-fumarate (TDF)-based regimens during pregnancy, TFV hair concentrations were analyzed using liquid chromatography/tandem mass spectrometry. Weight-normalized TFV concentrations were log10 transformed. Multivariable linear regression assessed correlates of TFV concentrations. RESULTS Overall, 121 mothers on TDF-based ART during pregnancy had hair specimens tested for TFV concentrations and were included in the analysis. Median age at delivery was 31 years (IQR 26-36); 71% self-identified as non-Hispanic black, and 10% had unsuppressed viral loads (VL) in late pregnancy (HIV-RNA ≥400 copies/mL). Median time from birth to hair collection was 3 days (IQR 1-14) and median TFV hair concentration was 0.02 ng/mg (IQR 0.01-0.04). In multivariable models, an unsuppressed VL in late pregnancy was associated with 80% lower adjusted mean peripartum TFV concentrations than pregnancies with viral suppression (95% CI: -90% to -59%, p < 0.001). Use of TDF only in the first trimester and attaining high school graduation were also associated with lower TFV hair concentrations. CONCLUSIONS Unsuppressed VL during late pregnancy was strongly associated with lower maternal TFV hair concentrations at birth, though viremia was rare. Efforts to improve maternal virological outcomes and eliminate vertical HIV transmission could incorporate drug exposure monitoring using hair or other metrics.