and suggests that antenatal testing could prevent a significant proportion ofvertical infection.In a recent survey of all obstetric units in the British Isles, 51% were offering HIV tests only to women perceived as being at risk, 3% to all women, and the remainder had no formal policy.3 Our results show that in south east England, only 17% of live births to infected women are recognised before delivery. There is therefore considerable scope for improvement in antenatal HIV testing programmes.We thank the obstetricians, midwives, paediatricians, and other physicians who have participated in the reporting schemes, microbiologists reporting HIV seropositive children to CDSC and CD(S), and T Berry for her clerical help. This study is supported by the AIDS Education and Research Trust (AVERT). The unlinked anonymous testing programme is supported by the Medical Research Council. The British Paediatric Surveillance Unit is supported by the Medical Research Fund of Children Nationwide.

and suggests that antenatal testing could prevent a significant proportion ofvertical infection.In a recent survey of all obstetric units in the British Isles, 51% were offering HIV tests only to women perceived as being at risk, 3% to all women, and the remainder had no formal policy.3 Our results show that in south east England, only 17% of live births to infected women are recognised before delivery. There is therefore considerable scope for improvement in antenatal HIV testing programmes.We thank the obstetricians, midwives, paediatricians, and other physicians who have participated in the reporting schemes, microbiologists reporting HIV seropositive children to CDSC and CD(S), and T Berry for her clerical help.

Correspondencerear of the vaporizer was loose and a minor adjustment corrected the reported problem. The nut behind the vaporizer is not an adjustment or adjustable. It is tightened at the factory and Loctite is applied to hold it in position. In excess of 90 inch pounds of force is required to break the nut free. We recommend only individuals trained on the servicing procedures of the Narkomed 4 attempt adjustments to the vaporizer mechanisms.There are no other reports of this failure mode in our complaint files and there are literally thousands of vapor-izers mounted on North American Drager machines worldwide. Our experience has been that if vaporizers are properly installed on the Narkomed 4 and adjusted in accordance with North American instructions the agent operates as intended.