It is known that nitrous oxide (N2O) inactivates vitamin B-12 and causes hyperhomocysteinemia. The personnel working at the operating theatres are repeatedly exposed to N2O in the ambient air. This prompted us to investigate the biochemical indices of vitamin B-12 metabolic status among female personnel working under various levels of N2O exposure. In this study, the homocysteine and folic acid levels were assessed and bad obstetric outcome was questioned. Sixty operating theatre female personnel were examined. Vitamin B-12 and folic acid, total homocysteine level, anticardiolipin IgM, IgG, antiphospholipid IgM, IgG levels were measured in serum. A questionnaire inquiring about obstetric history was given. The serum concentration of folic acid was 10 +/- 3.3 nmol liter(-1). The vitamin B-12 level was 332 +/- 134 pmol liter(-1), the serum concentration of homocysteine was 9.1 +/- 2.4 nmol liter-1 and all were within normal ranges. There was no difference regarding homocysteine, folic acid, vitamin B-12 levels and the obstetric history between the subjects who had abortus history and the subjects who had not abortus history. Exposure to N2O in healthcare workers was not associated with alterations of homocysteine, folic acid status and bad obstetric outcome (Tab. 4, Ref. 18). Text in PDF www.elis.sk.