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Mother-to-child transmission (MTCT) is by far the largest source of HIV infection in children below the age of 15 years. In countries where blood products are regularly screened and clean syringes and needles are widely available, it is virtually the only source in young children.

So far, the AIDS epidemic has claimed the lives of nearly 3 million children, and another 1 million are living with HIV today. World-wide, one in ten of those who became newly infected in 1998 was a child. Though Africa accounts for only 10% of the world’s population, to date around nine out of ten of all HIV-infected babies have been born in that region, largely as a consequence of high fertility rates combined with very high infection rates. In urban centres in southern Africa, for example, rates of HIV infection of 20- 30% among pregnant women tested anonymously at antenatal clinics are common. And rates of 59% and even 70% have been recorded in parts of Zimbabwe, and 43% in Botswana.

However there is no room for complacency elsewhere. African countries were among the earliest to be affected by HIV, and the epidemics on the sub-continent are therefore well advanced. But the virus is now spreading fast in other regions of the world, and every-where the proportion of women among those infected is growing.

Globally, there are around 12 million women of childbearing age who are HIV-positive. And the number of infants who acquire the virus from their mothers is rising rapidly in a number of places, notably India and South-East Asia.

The effects of the epidemic among young children are serious and far-reaching. AIDS threatens to reverse years of steady progress in child survival, and has already doubled infant mortality in the worst affected countries. In Zimbabwe, for instance, infant mortality in-creased from 30 to 60 per 1000 between 1990 and 1996. And deaths among one- to five-year-olds, the age group in which the bulk of child AIDS deaths are concentrated, rose even more sharply - from 8 to 20 per 1000 - in the same period.

1.1 The risk of MTCT

The virus may be transmitted during pregnancy (mainly late), child-birth, or breastfeeding. In the absence of preventive measures, the risk of a baby acquiring the virus from an infected mother ranges from 15% to 25% in industrialized countries, and 25% to 35% in developing countries. The difference is due largely to feeding practices: breastfeeding is more common and usually practised for a longer period in developing countries than in the industrialized world.

1.2 Prevention strategies

Until recently, countries had only two main strategies for limiting the numbers of HIV-infected infants:

· primary prevention of MTCT - taking steps to protect women of childbearing age from becoming infected with HIV in the first place;

· the provision of family planning services, and pregnancy termination where this is legal, to enable women to avoid unwanted births.

These remain the most important strategies for reducing HIV among young children and essential activities in all national AIDS campaigns.

Today, however, there is a third option for HIV-positive women who want to give birth which consists of a course of antiretroviral drugs for the mother (and sometimes the child), and replacement feeding for the infant. A recent trial in Thailand using a short course of zidovudine has shown that this strategy is able to reduce the risk of MTCT to below 10% when breastfeeding is strictly avoided. Alternative regimens using short courses of other antiretroviral drugs, sometimes in combination, will soon be available. Furthermore, trials are being conducted to find out what happens if mothers do subsequently breastfeed their babies instead of giving replacement feeds. This is a critical issue since the majority of HIV-positive women who risk transmitting the virus to their infants come from cultures where breastfeeding is the norm, and where replacement feeding presents great difficulties for many women.

Introducing a strategy of antiretroviral drug use and replacement feeding is, however, a complex process. To take advantage of the intervention, mothers need to know that they are HIV-positive, and they must therefore have access to voluntary counselling and testing. Costs and benefits need to be carefully assessed. Policy-makers need to decide what kind of programme is feasible and most appropriate for their countries, and whether or not to test models of the strategy in pilot projects before introducing it more widely. Such a programme requires a commitment to ensuring there is an efficiently functioning primary health care system with certain key services as a basis for introducing the strategy. Where these conditions do not already exist, decisions need to be made about how to strengthen the health infrastructure, what time-frame would be realistic, and what else is needed to create the conditions for safe and successful introduction of antiretroviral drugs and replacement feeding.

The purpose of this paper is to review the key issues for consideration in policy-making, and to propose ways in which the strategy might be tailored to suit local conditions. The paper is intended for all those with a part to play and a special interest in national policy making with respect to HIV prevention and care.

1.3 The cost of inaction

The cost of doing nothing to reduce MTCT will depend a great deal on the prevalence of HIV infection among parents-to-be. In areas where 20% or more of pregnant women are HIV-positive, the financial cost of caring for sick and dying HIV-infected children will be enormous, and there will be significant loss of the benefits from the huge commitment of time, energy and resources spent on reducing child morbidity and mortality over recent decades. Where HIV prevalence is low, health care costs will be relatively low too, and the waste of resources already spent on child survival not quite so dramatic. However, the costs for families and communities cannot be measured in financial terms alone, and many couples will bear responsibility for looking after their infected babies, often while struggling to cope with their own ill-health.