A woman on antiretroviral (ARV) therapy before becoming pregnant should be able to continue treatment throughout the pregnancy, although the particular drugs in the regimen or dosing might be changed. If not on ARV therapy, immune status needs to be monitored throughout the pregnancy. The use of ARVs should be considered at some point to reduce the risk of transmission. 

Transmission can occur any time during pregnancy, labour, or after delivery through breastfeeding. Several factors are associated with a higher risk of transmission, including the maternal viral load and CD4 cell count.

In the absence of any intervention, an HIV-positive woman has a 15 to 30% chance of transmitting the virus to her baby during pregnancy and delivery. If she breastfeeds, there is an increased 5 to 20% risk of transmission. With ARV treatment, the risk of vertical transmission can be reduced to under 2%. 

In the developed world, widespread use of antiretroviral therapy during pregnancy has been associated with a dramatically reduced incidence of mother-to-child transmission among women with HIV who do not breastfeed. Similar success is seen in under-resourced areas where prenatal care and access to antiretrovirals is provided.

There is little evidence to date that antiretroviral drugs cause a significant risk of serious abnormalities; however, the long-term safety of exposure to antiretroviral drugs in the womb and early in life is not known. The U.S. guidelines point out that risk depends not just on the drug itself, but the dose of the drug used, the gestational age of the foetus at exposure, duration of exposure, interaction with other agents, and perhaps, the effect of the mother and foetus' genetic make-up.^[1]

The management of any HIV-positive pregnant woman requires a careful consideration of the balance between the mother's health needs, locally available treatment options, the need to reduce transmission, and the adverse effects of antiretroviral therapy. Recommended treatment options vary by country and local resources.

Most women in the developed world choose to feed their child with infant formula. However, in resource-limited settings, replacement feeding is not always a viable option because of the lack of safe water or a reliable supply of infant formula.

In areas where malnutrition and childhood illness are common, infants who are not breastfed are more likely to die from other causes. Making the choice not to breastfeed can also lead to stigmatisation, as in societies where breastfeeding is the norm, not to do leads to speculation about the mother's health status.

Early weaning was a strategy explored to lessen the risk of MTCT, but it does not seem to improve HIV-free survival time or infant morbidity or mortality.

In prevention of mother-to-child transmission (PTMTC), some of the issues being studied are:

• The effect, if any, of HAART on the rate of low birth weight and preterm labour.
• The viral dynamics of HIV in breast milk.
• The use of ARVs, by the mother or infant, to lower the risk of transmission while breastfeeding.
• Whether there is a heightened incidence of proinflammatory response and immune reconstitution syndrome in women after giving birth. 
• Whether the use of ARVs in general, or particular drugs or drug classes, increases the incidence of birth defects.
• Strategies for preventing drug resistance.

Guidelines consulted in preparation of this section are available for download from the internet. They are: Antiretroviral drugs for treating pregnant women and preventing HIV infection in infants, prepared by the World Health Organization in 2006 and available at http://www.who.int/hiv/pub/guidelines/pmtctguidelines3.pdf 

Public Health Task Force recommendations for use of antiretroviral drugs in pregnant HIV-1 women for maternal health and interventions to reduce perinatal HIV-1 transmission in the United States, prepared in 2006 and available at http://aidsinfo.nih.gov/ContentFiles/PerinatalGL.pdf. 

The British HIV Association (BHIVA) is in the process of seeking consultation on their guidelines, Management of HIV infection in pregnant women (2007) and that document can be obtained from their website at http://www.bhiva.org/cms1220627.asp