According to a National Institutes of Health (NIH) Study, infants exposed in the womb to the HIV drug tenofovir disoproxil fumarate, may have lower bone mineral content than those exposed to other anti-HIV drugs. The study appears in the journal Clinical Infectious Diseases.

The study included a total of 143 infants, of these participants 74 were exposed to tenofovir in the uterus, while 69 were given other anti-HIV drugs. Using DXA scans, researchers measured bone mineral content within the first four weeks of birth. Pregnant women who were exposed to tenofovir in their third trimester gave birth to babies whose bone mineral content was 12% lower than that of infants not exposed to this drug in the uterus.

While the authors say the study results are concerning, they caution against making therapy changes. Tenofovir has been proven successful in treating HIV in pregnant women and is often used to prevent HIV transmission to infants. It is also unknown whether the lower bone mineral content is abnormal and will increase the risk of fractures or whether these children with regain bone mineral content as they get older.

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“At this point, we can say that those who care for pregnant women with HIV and their children should be aware that prescribing tenofovir to pregnant women could be a concern for their infants’ bones,” said George K. Siberry, MD, the first author of the study and medical officer with NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). “Families should keep in close touch with their physicians to monitor their child’s bone development.”

Additional studies will need to be conducted to better understand how the drug affects bone health in children born to mothers exposed to tenofovir during pregnancy.

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