For 25 years epidemiological studies have associated occupational exposure to anaesthetic gases with a range of health effects, including neurological, renal, and hepatic disease; reduction in mental performance and manual dexterity; and increased risk of spontaneous abortion and congenital abnormalities in offspring.1 Most attention has been focused on studies in the 1970s into the outcome of pregnancy among theatre workers, and these undoubtedly stimulated the Department of Health's guidance recommending improvements in the ventilation of operating theatres and the introduction of scavenging systems.2

These environmental improvements, coupled with methodological criticisms of the early reports, have tended to dispel concern. A major 10 year prospective study of 11 000 women doctors in the United Kingdom, which followed them through 13 500 pregnancies till 1986, was also reassuring (R P Knill-Jones, personal communication, 1992). This study did not confirm the earlier work of the 1970s and showed no relation between hours spent in theatre, medical specialty, and reported miscarriages after confirmed pregnancy. Nor was any increase in congenital malformations …