HIV testing in pregnancy - the background

In order to become pregnant, a woman may put herself at risk of HIV infection by having unprotected sex. If she is already HIV-positive, or becomes infected at the time of conception or later, there is a risk to her unborn child. This risk, in the UK, is currently a one in seven chance the baby will be infected (assuming that no preventative measures were taken); that is, for every seven babies born to HIV-positive women, six will not be infected.

In the past there have been concerns about the value of testing for a disease which is highly stigmatised and for which there is no cure. However, interventions are now available which have proved highly effective at reducing the risk of transmission to the baby and which may be beneficial for the woman in her own right. These interventions are:

• Offering antiretroviral therapy to the mother during pregnancy and labour, and to the infant for one month after birth.
• Offering caesarean section rather than vaginal delivery. When caesarean delivery was used alongside AZT the risk of vertical transmission was further reduced by 50% compared with AZT treatment alone. When caesarean delivery was used without antiretroviral therapy it still resulted in a reduction in risk (10% transmission risk compared with 19% transmission risk amongst mothers who did not deliver by caesarean and did not take AZT). However, some studies suggest that caesarean section may be unnecessary if viral load is well controlled (below detection) during pregnancy.
• Advising against breastfeeding. Several studies have shown that women who breastfeed are more likely to transmit HIV to their baby.

Many professionals feel that pregnant women should be tested because these interventions have had a dramatic effect in reducing vertical transmission.

However, whilst no one would dispute the desire to prevent vertical transmission, some professionals believe that the rights of the pregnant woman as a person in her own right could be compromised if HIV testing in the antenatal clinic is not introduced with care and sensitivity. Informed consent for the HIV antibody test is a pre–requisite for any person considering it. For the pregnant woman, her decision is particularly complex. The experience of finding out a positive diagnosis at any time is very painful, even if anticipated. During pregnancy, it is likely to be more so.

It is likely to have a more profound effect on the family than at any other time. The father's HIV status will be in doubt, and the unborn child's status will be unknown. The HIV status of other children in the family might also be called in question. While there is still considerable stigma attached to HIV many women are very fearful of the test, whatever the result might be. This can act as a disincentive to accepting antenatal care.

It is also the case that most babies born to HIV–positive women will be HIV–negative. The interventions offered to reduce the risk of vertical transmission are not without side-effects and do not offer 100% protection.

The long-term effects of anti-HIV drugs on an HIV–negative child are not known, although follow–up of mother–infant pairs treated with AZT has consistently shown no long–term effects. However, a review of 30 mother–infant pairs treated with dual or triple therapy demonstrated a higher than average rate of premature delivery, and nine cases of anaemia in infants exposed to AZT/3TC. Caesarean section is also not without danger for the mother. These risks must be balanced against the proven effectiveness of anti-HIV therapy in reducing transmission, and the well- established health consequences of being born HIV-positive.

See The HIV & AIDS Treatments Directory, or aidsmap.com, also published by NAM, for extensive discussion of research in this area.