The current antenatal HIV screening system fails to take into account the ongoing risk of exposure, warn doctors in this week's BMJ.

Last month, the BMJ reported that rates of mother to child transmission of HIV are dramatically reduced by antiretroviral use, caesarean section, and avoidance of breastfeeding. However, none of these interventions can take place without awareness of the mother's HIV status, argue two senior doctors from Warwickshire Hospital in Coventry.

In the United Kingdom, all antenatal clinics routinely offer HIV testing. Most mothers accept screening, but two recent cases, they say, highlight the deficiencies in the existing system.

In 2006, two infants were diagnosed with HIV within a few weeks of one another. Both mothers had had antenatal screening, and both tested HIV negative.

The authors warn that women who seroconvert during pregnancy (develop antibodies in their blood as a result of infection) are at a greater risk of transmitting HIV to their babies as the mother's viral load is at its highest at this stage.

Alternatively, they explain, both patients may have been tested during the serological window period (the stage immediately after infection when the virus cannot be detected).

They point out that the information leaflet on HIV testing produced by the Department of Health does not include an explanation about the HIV window period, and retesting is not routinely offered to those at higher risk.

Following these two cases, local antenatal services have altered their HIV testing policies to offer repeat testing of high risk individuals at 32 weeks of pregnancy and midwives are being advised to consider ongoing risks in all women, they say.

Contact tracing as is currently offered to HIV positive women should be offered to high risk HIV negative women as well.

They also suggest that high risk women who initially refuse testing in pregnancy should be offered counselling by trained health advisers, with mechanisms in pace to offer testing again later in their pregnancy.

"We see this as a safety net for those let down by the current antenatal system," they conclude.

Letter: HIV and pregnancy: Are we doing enough?
BMJ Volume 334 pp 1287-8
bmj