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  21st Conference on Retroviruses and
Opportunistic Infections
Boston, MA March 3 - 6, 2014
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Newborns Exposed to TDF in Utero Have Lower Bone Mineral Content in US
  CROI 2014, March 3-6, 2014, Boston
Mark Mascolini
HIV-uninfected US infants born to HIV-positive mothers who took tenofovir (TDF) during the third trimester had significantly lower whole-body bone mineral content (BMC) than infants born to mother who did not take TDF [1]. This difference persisted after statistical adjustment for numerous factors that may affect BMC in infants, but whether the deficit persists is unknown.
Both US and World Health Organization guidelines recommend TDF for pregnant women. The potential impact of TDF on bone mineral density is well appreciated in adults and children taking this antiretroviral but has not been closely studied in infants exposed to TDF in utero. Pediatric HIV/AIDS Cohort Study (PHACS) researchers conducted this analysis of HIV-uninfected infants exposed or not exposed to maternal TDF.
All infants had a gestational age of 36 weeks or more. In the TDF arm, infants were exposed to TDF for 8 or more weeks in the third trimester. In the no-TDF arm, infants were not exposed to TDF at any point. Infants had whole-body BMC analyzed by DXA scan between 0 and 4 weeks after birth.
The analysis involved 74 TDF-exposed infants and 69 unexposed infants seen at 14 sites in 9 states and Puerto Rico. Median maternal age was 30 in the TDF arm and 28 in the no-TDF arm, while 70% and 58% of mothers on or off TDF were black and 19% and 32% Hispanic. Most women in the TDF arm (86%) and the no-TDF arm (64%) took a boosted protease inhibitor (PI) during pregnancy, and 26% and 37% respectively reported any substance use. Almost all women in both arms had a third-trimester CD4 count above 250 and a viral load below 400 copies. Infants born to mother taking TDF did not differ significantly from the control group in gestational age, birth length z score, birth weight z score, or proportion of girls.
Whole-body BMC averaged 56.0 g in the TDF group and 63.8 g in the no-TDF group, a significant difference of 7.8 g (P = 0.002). In an analysis adjusted for (1) study site, (2) infant gestational age, body length, race/ethnicity, and age at DXA, and (3) maternal boosted PI use, age, and smoking status, whole-body BMC was 6.4 g lower in the TDF group (95% confidence interval 2.1 to 10.7, P = 0.004).
Neither maternal CD4 count nor viral load in the third trimester differed between the two study arms. The researchers found no associations been maternal CD4 count or viral and infant BMC. As a result, the PHACS investigators concluded that maternal CD4 count and viral load are not likely to account for the link between TDF exposure and BMC if the effect occurs during the third trimester.
The researchers stressed that this is a nonrandomized cross-sectional analysis, and whether the impact of maternal TDF on newborn BMC persists is unknown. Strengths of the study include use of DXA scanners made by the same company, training of all scanners by the same person, and centralized DXA scan analysis.
The PHACS team called for longitudinal studies to assess the duration and clinical significance of their finding. They noted that IMPAACT P1084s, an ongoing study in Africa, includes serial infant DXA after randomized maternal assignment to TDF or a no-TDF regimen.
1. Siberry GK, Jacobson DL, Kalkwarf H, et al. Lower newborn bone mineral content associated with maternal use of tenofovir disoproxil fumarate. CROI 2014. Conference on Retroviruses and Opportunistic Infections. March 3-6, 2014. Boston. Abstract 71.