Low maternal vitamin D increases risk of HIV transmission to child and infant mortality

Low maternal vitamin D is associated with an increased risk of mother-to-child HIV transmission and child mortality, investigators report in the online edition of the Journal of Infectious Diseases.

“An increased risk of being HIV infected or of dying at birth was observed for children born to women with a low vitamin D level at baseline; a low maternal vitamin D level was also associated with HIV transmission via breast-feeding and with higher infant mortality during follow-up”, write the investigators.

It is already known that vitamin D levels can affect the functioning of the immune system and that maternal vitamin D levels have an impact on foetal growth. Furthermore, vitamin D supplementation has been shown to improve the outcome of tuberculosis therapy, which is significant in the context of HIV as tuberculosis is the single most important cause of illness and death in HIV-positive individuals.

There has, however, been little research into the impact of vitamin D levels in HIV-positive pregnant women and outcomes including adverse birth events, mother-to-child HIV transmission, infant death during the early months of life, or HIV transmission because of breastfeeding.

A study into the use of vitamin supplementation in HIV-positive women in Tanzania provided investigators with an opportunity to assess the importance of maternal vitamin D levels on such outcomes.

A total of 884 women were included in the researchers’ analysis. Most (80%) had asymptomatic HIV disease. Vitamin supplementation was initiated between weeks twelve and 27 of pregnancy. This did not, however, include vitamin D, levels of which were assessed at baseline.

No association was detected between vitamin D levels and adverse pregnancy outcomes such as premature delivery, or having a baby with a low birth weight, or that was small for its gestational age.

However, low baseline maternal vitamin D (below 32 ng/ml), was associated with a 49% increase in the risk of foetal death or HIV transmission at birth (95% CI, 7% - 109%), compared to the infants of mothers with sufficient vitamin D levels.

In addition, the infants of mothers with low vitamin D had a 50% increase in their risk of being HIV-infected at six weeks of age compared to the children of mothers with normal vitamin D (95% CI, 1.02-2.20).

After 24 months of follow-up, 30% of infants were HIV-positive. The children of mothers with insufficient vitamin D who were HIV-negative at six weeks of age had a two-fold increase in the risk of acquiring HIV from their mothers during breastfeeding than did infants whose mothers had adequate vitamin D (incidence rate ratio [IRR], 2.03; 95% CI, 1.08-3.82).

The overall rate of mother-to-child HIV transmission after 24 months was 46% higher in the infants of mothers with deficient vitamin D than it was in the children of mothers with normal levels of this vitamin.

Further analysis by the investigators showed that mothers with the lowest levels of vitamin D had the highest risk of mother-to-child transmission (p = 0.01), and that this risk decreased as maternal vitamin D increased.

Finally, the researchers found that low maternal vitamin D increased the risk of infant death during follow-up.

“Vitamin D is known to contribute to the development of the foetal immune system; a stronger immune system may be more resistant to HIV infection and may explain the decreased risk of mother-to-child transmission observed”, comment the investigators.

They continue, “this finding would also likely correlate with fewer infections and opportunistic illnesses during follow-up and, consequently, with decreased mortality. In addition, there is increasing evidence supporting the role of vitamin D in fighting tuberculosis; tuberculosis is one of the primary killers in HIV-infected populations.”

The investigators conclude that should vitamin D supplementation be shown to be effective in studies it “could prove to be a relatively simple and inexpensive method to lower mortality among children and to help prevent mother-to-child transmission of HIV as a adjunct to HIV therapy.”