Editor,—Since 1992 Department of Health guidelines have recommended that HIV screening be offered to all pregnant women in areas of high seroprevalence¹ but implementation and uptake has been poor. In 1998 an intercollegiate working party recommended that HIV testing be integrated with antenatal screening for other infections and that the test should be offered and recommended to all pregnant women in high seroprevalence areas.² In 1999 the Department of Health extended these recommendations to all regions aiming to reduce neonatal HIV infection by 80% by 2002.³ We present the case of an infant with symptomatic HIV infection, whose mother's antenatal HIV test was negative and discuss the implications.

A 3 month old female, born at term by spontaneous vaginal delivery and breastfed, presented with a 1 week history of increasing respiratory difficulty. Following further deterioration, she was transferred to St Mary's Hospital and ventilated. Pneumocystis carinii pneumonia (PCP) was diagnosed on bronchoalveolar lavage. Anti-HIV antibodies were present in serum and HIV infection was confirmed by the detection of HIV-DNA in peripheral blood mononuclear cells (PBMC) by PCR amplification. HIV-1 infection was confirmed in both parents. Her asymptomatic mother had received antenatal care from the 12th week of gestation and was HIV seronegative at 29 weeks. To investigate a possible false negative result, other sera stored at various times were retrieved and tested. The results, which show seroconversion late in pregnancy, are summarised in table 1.

The HIV antibody test is usually performed at the booking visit with other routine antenatal screens. This allows the parents time to adjust to the diagnosis before delivery, to consider family planning issues and interventions to minimise the risk of mother to child transmission. In addition, mothers with advanced immunosuppression benefit from antiretroviral therapy.

Although rarely reported, an HIV seronegative mother whose partner has undiagnosed HIV infection is at continued risk of infection. This may become more common in the United Kingdom as heterosexual intercourse is now the most common risk for HIV infection in newly diagnosed patients.⁴ Primary HIV infection during gestation or lactation is associated with an increased risk of mother to child transmission.⁵

Repeat antenatal screening late in pregnancy, as is recommended for syphilis in the United States,⁶ would identify some primary HIV infections during gestation. However, if maternal infection is not prevented transmission during lactation would remain a risk and there would be significant logistic and cost implications. The extension of testing for HIV (and other infections) to the partners of pregnant women is appealing as both maternal and infant infections could be prevented (and the infected male may benefit from earlier diagnosis and treatment) but would require a fundamental change to antenatal care. A practical approach, which may prevent maternal and neonatal infection (but not identify the infected male) is to use the opportunity, when giving negative HIV, hepatitis B, and syphilis results to the mother, to discuss the sexual transmission of infections, to emphasise that the negative results cannot be extrapolated to the partner, and advocate safer sex which is commonly abandoned following conception.