There are three main ways that mother to child infection occur; the child may acquire HIV while the mother is carrying it, while giving birth or after birth, primarily by breast-feeding.
Research into the primary modes of mother to fetus transmission is ongoing. Risk factors include: maternal viral load (the amount of active virus in a pregnant woman), vaginal delivery, and breast-feeding. Results of a ground breaking study offers important information about one possible factor in mother-to-infant HIV transmission. The study also suggests questions for further investigation. (In this article, "mother-to-infant" transmission of HIV will be called: "vertical transmission")
The Vitamin-A Question
Researchers asked: could poor diet and nutrition during pregnancy increase the risk of vertical transmission? Could a deficiency of Vitamin A in HIV+ pregnant women make it more likely that a baby will acquire HIV from its mother? Vitamin A is known for stimulating immune response and protecting mucosal tissues.
(Immune Response: The activity of the immune system against foreign substances. Mucosal Tissue: A moist layer of tissue that lines body cavities which have an opening, e.g., lining of the mouth, anus, or vagina.)
A team of researchers did the study with HIV+ pregnant women who were patients at a local Hospital in Malawi, Africa. Consenting women who visited the hospital's prenatal clinic between Nov. '89 & August '91 were tested for HIV.
Three hundred and thirty eight HIV+ pregnant women formed the core group. Researchers gathered complete data on them. During their first prenatal visit, clinicians collected and stored blood serum. Levels of Vitamin A in serum were determined. For a subset of women, CD4 & CD8 counts were determined at the first visit. (CD4 and CD8 counts were obtained from the other women after delivery.)
Regular follow-up visits with moms and infants were every 3 months for one year. When the babies were 1 year old, they were tested for HIV. Follow-up tests at 18 months confirmed that all the babies had lost maternal antibodies. (Babies acquire antibodies from their mothers, detectable by blood tests. Children usually lose maternal antibodies by 1 year of age, when the child's immune system has become capable of actively producing its own antibodies.)
Researchers compared moms of HIV positive babies to moms of HIV negative babies, with emphasis on the Vitamin A status of the mother. An adequate Vitamin A level was defined as more than 1.05 micro moles per liter.
Three hundred eighty one infants were tested for HIV at 2 months. Fourteen had indeterminate test results; 84 were HIV+, 283 were HIV-. The rate of transmission among moms whose infants survived to 1 year was 21.9%.
Data on the serum level of Vitamin A was available for 338 mothers. The moms of HIV+ kids and those of HIV- kids had similar traits. But, the average level of Vitamin A for moms of HIV+ infants was 0.83 mm/liter compared to 1.07 for moms of HIV- infants.
Total lymphocyte count, maternal CD4 count, CD4% & CD4/CD8 ratios were lower in mothers who gave birth to HIV+ infants than in mothers who did not.
One hundred and ninety-six of the 338 mothers were found to be Vitamin A deficient (serum levels below 1.05 mm/liter). The "mean" (average) serum Vitamin A level for all (338) women was 1.02 mm/liter.
Mothers were grouped into 4 categories, based on their level of serum Vitamin A, (measured in micro moles per liter:)
- Vitamin A levels: 0.70 or less
Transmissions Rate: 32%
- Vitamin A levels: 0.70-1.05
Transmission Rate: 26%
- Vitamin A levels: 1.05-1.40
Transmission Rate: 16%
- Vitamin A levels: 1.40 or more
Transmission Rate: 7%
("The relative risk of transmitting HIV to their infant "increased with decreasing serum Vitamin A"
Mothers whose children died before their first birthdays had the lowest average serum levels of of any subgroup. The Vitamin A level for these moms was 0.78 mm, not very different from moms of HIV+ babies, which was 0.86 mm. Both figures are much lower than the "mean" Vitamin A level for mothers of HIV- babies (1.07 m m/liter).
Overall, Vitamin A deficiencies were "associated with a threefold to fourfold increased risk of mother-to-child transmission of HIV." This clearly suggests a relationship between nutrition and vertical transmission of HIV.
Low Vitamin A levels can cause impaired lymphocyte functioning, which may cause a higher viral burden in pregnant women. Deficiencies are associated with the destruction of mucus and certain cells, which may damage placenta. Mucosal damage could make the birth canal more susceptible to trauma, increasing the amount of blood an infant is exposed to during birth, increasing risk of transmission.
Note: "although our study showed that Vitamin A deficiency was associated with increased mother-to-child transmission of HIV, we cannot attribute these findings to lack of Vitamin A alone, other micro nutrient abnormalities may act as cofactors." HIV can cause altered levels of other nutrients; Vitamins E, B, copper & zinc.
Sixty-five percent (65%) of the women in this study were Vitamin A deficient. Vitamin A deficiencies are common in HIV+ pregnant women for a number of reasons, including pregnancy itself. Or not taking in or absorbing enough foods with Vitamin A, & some opportunistic infections can cause Vitamin A depletion.
Most of the women were in early stages of HIV. Advancing HIV is associated with declines in Vitamin A, thus, future pregnancies may be accompanied by greater deficits of Vitamin A, & higher rates of transmission.
Vertical transmission rates were much higher in moms who were Vitamin A-deficient.
Given the relationship between Vitamin A deficiency & risk of transmission, doctors propose investigating repletion of Vitamin A during pregnancy as an inexpensive & simple way for reducing HIV infant risks. This study definitely warrants further investigation of its central findings and implications.
Semba RD and others. Maternal Vitamin A deficiency and mother-to-child transmission of HIV-1. The Lancet 343: 1593-1597. June 25, 1994. Further Summarized by Nancy MacNeil from Sept. Issue Beta '94 (Leslie Hanna).