Offer second HIV test late in pregnancy to women with high HIV risk

Two instances of mother-to-child transmission of HIV occurred in the United Kingdom because the mothers either became infected with HIV during pregnancy, or had their HIV screen during the ‘window period’ before the body has yet produced antibodies to the infection. The cases are reported in the June 22^nd edition of the British Medical Journal and the authors, from the hospital in Coventry which treated the women, recommend that women from groups with a high risk of HIV should be offered a second HIV test at the 32^nd week of pregnancy.

The risk of mother-to-child transmission of HIV can be reduced to very low levels by the appropriate use of antiretroviral therapy during pregnancy, by intervening during labour if need be, and by the avoidance of breastfeeding. But to offer these interventions it is first necessary to establish if a mother is infected with HIV.

Since 1999, all pregnant women in the UK have been offered an opt-out HIV test as part of their antenatal care. Official statistics suggest that almost 98% of pregnant women in Coventry accept this offer of an HIV test.

However, in October 2006 two six month-old infants were diagnosed with HIV. Both mothers had been screened for HIV during pregnancy and tested negative.

The treating physicians are concerned that the transmissions occurred because the current testing recommendations fail to take into account the risk of a mother becoming infected with HIV during pregnancy. This is particularly worrisome as seroconversion during pregnancy is associated with a higher risk of HIV transmission to the infant.

Both the Coventry transmission cases involved mothers whose routine HIV pregnancy tests were negative. However, the women had partners from regions with a high HIV prevalence and doctors suggest that the women may have been infected with HIV during pregnancy. An alternative explanation could be that both mothers were tested during the ‘window period’ before their bodies developed an antibody response to HIV.

Following these two cases, all women thought to have a high risk are retested for HIV at 32 weeks of pregnancy. The doctors write: “The current cost of an individual HIV test is around £1. The projected lifelong cost of antiretroviral treatment alone for one HIV-positive child is in the order of £1 million. The physical and psychological trauma to both the child and the family as a whole is immeasurable.”