Phosphaturia in HIV-Exposed Uninfected Neonates Associated with Maternal Use of Tenofovir Disoproxil Fumarate in Late Pregnancy.

Background: Tenofovir disoproxil fumarate (TDF) is often used in treating pregnant women living with HIV. Third-trimester TDF exposure is associated with a 12% reduction in bone mineral content in HIV-exposed uninfected (HEU) neonates. The potential mechanisms underlying this observation are unknown.

Methods: The TDF study enrolled newborns of gestational age ≥36 weeks from the Surveillance Monitoring for Antiretroviral Therapy and Toxicities study based on in utero TDF exposure (TDF use ≥8 weeks in the third trimester vs none). Blood and urine samples were collected cross-sectionally within 30 days of birth to assess renal function (serum creatinine, serum phosphate, eGFR, percent tubular reabsorption of phosphate [PTRP]), and bone turnover (serum parathyroid hormone, 25-OH vitamin D [25(OH)D], and urinary cross-linked N-telopeptide of type 1 collagen). For each biomarker, a LOESS plot was fit using values at age at specimen collection; regression lines over age were fit among samples collected from 4 to 30 days, to compare slopes by TDF exposure.

Results: Among 141 neonates, 77 were TDF-exposed and 64 TDF-unexposed. Between age 4 and 30 days, PTRP decreased more rapidly in the TDF-exposed compared to the unexposed group with slopes of -0.58 vs -0.08/day (difference -0.50/day [95% CI -0.88, -0.11]). Slopes for 25(OH)D were similar in both groups, but serum levels were lower in TDF-exposed neonates (median [IQR]: 22 [19, 29] vs 26 [22, 37] ng/mL). No differences were observed for other biomarkers.

Conclusions: Third-trimester in utero exposure to TDF is associated with increased urinary loss of phosphate and lower serum concentrations of 25(OH)D in HEU neonates.