Executive summary
Breastfeeding is the best food for infants, and is an effective method of reducing the risk of
common childhood morbidity, particularly gastrointestinal and respiratory infections, and of
promoting child survival and maternal health through child spacing. In 2001, the World
Health Assembly endorsed the recommendation that infants should be exclusively breastfed
for the first six months of life to achieve optimal growth, development and health. Thereafter,
infants should receive nutritionally adequate and safe complementary foods while
breastfeeding continues to 24 months or beyond.
While breastfeeding carries significant health benefits to infants and young children, HIV can
be transmitted during breastfeeding from an HIV-infected mother to her infant. The reduction
of this transmission is one of the most pressing public health dilemmas confronting
researchers, health-care professionals, health policy-makers and HIV-infected women in
many areas of the world, especially in developing countries.
From the beginning of the HIV pandemic to 2006, 2.3 million children aged less than 15 years
worldwide were living with HIV and an estimated 530 000 children aged less than 15 years
were newly infected with HIV in 2006 alone, nearly always through mother-to-child
transmission (MTCT). HIV/AIDS is an increasingly important cause of mortality in those
aged less than five years in Africa. Before the highly-active antiretroviral therapy (HAART)
era, child mortality due to HIV was estimated to be 35.2% by age one year and 52.5% by two
years of age.
Mother-to-child transmission of HIV can occur during pregnancy, labour or delivery, or
through breastfeeding. Without specific interventions, HIV-infected women will pass the
virus to their infants during pregnancy or delivery in about 15–25% of cases; and an
additional 5–20% of infants may become infected postnatally during breastfeeding, for an
overall risk of 30–45%. Breastfeeding may thus be responsible for one third to one half of
HIV infections in infants in settings where interventions are not available (e.g. some countries
in Africa).
HIV has been detected in breast milk in cell-free and cell-associated compartments and there
is now evidence that both compartments are involved in transmission of HIV through breast
milk. This fact supports the idea that treatment to prevent MTCT should target the proviral
cell-associated HIV reservoir. Following ingestion of HIV infected breast milk, infant gut
mucosal surfaces are the most likely site at which transmission occurs.
The rate of late postnatal transmission (that is, after six weeks of age) can be better quantified
in 2006 than previously. Most transmission of HIV through breastfeeding occurs early in the
postnatal period, although transmission continues throughout the breastfeeding period. Data
from a meta-analysis show that the cumulative probability of late postnatal transmission at 18
months is 9.3% (95% confidence interval, CI, 3.8–14.8%). Late postnatal transmission,
therefore, could contribute as much as 42% to the overall rate of MTCT. Analysis indicates
that late postnatal transmission risk is around 1% per month of breastfeeding and is constant
over time from between four and six weeks to 18 months. Transmission can take place at any
point during breastfeeding, and the longer the duration of breastfeeding, the greater the
Literature review on HIV and Infant feeding 10
cumulative additional risk. When breastfeeding is prolonged beyond 18–24 months, the
additional cumulative postnatal HIV risk varies from 4% to 16% across studies, depending on
breastfeeding duration.
The risk of postnatal transmission through breastfeeding is associated with clinical,
immunological and virological maternal factors and infant feeding patterns. Maternal
seroconversion during breastfeeding, low maternal CD4 cell count, increased maternal RNA
viral load in plasma and breast milk and a lack of persistence of HIV-specific IgM in breastmilk
at 18 months are strongly associated with increased risk of transmission through
breastfeeding. Breast pathologies such as clinical and subclinical mastitis, nipple bleeding,
and abscesses, fissures or lesions are also associated with a higher risk of transmission
through breastfeeding. Exclusive breastfeeding for up to six months, however, is associated
with a three to fourfold decreased risk of transmission of HIV compared to non-exclusive
breastfeeding; mixed feeding, therefore, appears to be a clear risk factor for postnatal
transmission. One study found that about 4% of exclusively breastfed infants became infected
through exclusive breastfeeding from six weeks to six months. The duration of breastfeeding
is confirmed to be one of the main risk factors for HIV transmission through breastfeeding. In
Zimbabwe, among the children exposed to HIV through breastfeeding, the overall risk of
postnatal transmission was 12%, of which 68% occurred after six months.
Prevention of MTCT of HIV using available peripartum antiretroviral interventions can be
achieved leading to peripartum HIV transmission rates below 5%, even in breastfed
populations, and considerable effort is ongoing to expand these interventions to a wider
population. However, in settings where breastfeeding beyond one year is the norm, postnatal
transmission through breastfeeding reduces gains achieved by perinatal antiretroviral
interventions.
The incidence of HIV infection among women during the postpartum period is high in Africa.
The overall risk of MTCT is increased in recently-infected lactating women and estimated to
be 29% (95% Cl, 16–42%), illustrating the importance of prevention of primary infection.
HIV-prevention interventions directed at pregnant and lactating women could contribute to
reducing MTCT in several settings.
The most appropriate infant feeding option for an HIV-infected mother depends on her
individual circumstances, including her health status and the local situation. The health
services available and the counselling and support she is likely to receive should be
considered. The World Health Organization (WHO) recommends HIV-infected women
breastfeed their infants exclusively for the first six months of life, unless replacement feeding
is acceptable, feasible, affordable, sustainable and safe for them and their infants before that
time. When those conditions are met, WHO recommends avoidance of all breastfeeding by
HIV-infected women.
To help HIV-positive mothers make the best choice, they should receive appropriate
counselling that includes information about the risks and benefits of various infant feeding
options based on local assessments, and guidance in selecting the most suitable option for
their own situation. Counselling, information provision and support during the antenatal
period is key for women to make informed choices. Postnatal follow-up with repeated growth
measurements is also crucial to this support, as is nutritional counselling, particularly around
the period of breastfeeding cessation.
Literature review on HIV and Infant feeding 11
Early cessation of breastfeeding could also prevent a sizable proportion of postnatal HIV
infections but several studies in Africa have reported that it was associated with an increased
risk of infant morbidity (especially diarrhoea) and mortality in HIV-exposed children. Recent
data from Zambia and Botswana show that prolonged breastfeeding of children already
infected with HIV is associated with improved survival compared to early cessation of
breastfeeding.
It is also important to identify approaches to treating expressed breast milk to eliminate the
risk of transmission while preserving the milk’s nutritional content and protective qualities.
With this aim, expressed heat-treated breast milk and microbicides to treat HIV-infected
breast milk may have a role to play in shortening the duration of breastfeeding and allowing
for a safe transition period to other types of foods.
More research is required to provide practical tools that can be used routinely – especially
around the time of early breastfeeding cessation – to contribute to the assessment of the
nutritional adequacy of complementary feeding and guide efficiently the nutritional
counselling of children exposed to HIV.
Other possibilities for preventing HIV from being transmitted through breast milk are
emerging. These include giving HAART to women during breastfeeding (whether or not
necessary for the mother's health) and post-exposure prophylaxis to the infant. Recent studies
have sought to determine the effects of the former, and several studies on the latter are
ongoing; both are discussed in this review. Finally, passive and active immunization strategies
of breastfed newborns are increasingly being studied. Further research on their potential role
in reducing MTCT of HIV is needed and ongoing.
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