Risk of spontaneous abortion in women occupationally exposed to anaesthetic gases: a meta-analysis.
Tóm tắt
OBJECTIVES: To determine the association between maternal occupational exposure to anaesthetic gases and risk of spontaneous abortion. METHODS: A meta-analysis was performed of published epidemiological studies identified from literature reviews, unsystematic perusal of reference lists of relevant publications, and two Medline searches (1984-92, keywords: anaesthetic gases; anaesthetics; anaesthetics, local; operating rooms; operating room nursing; pregnancy; abortion; 1985-92, keywords: anaesthetics; adverse effects; occupational exposure; anaesthesia, inhalation; operating room nursing; pregnancy; abortion). All peer reviewed studies were retained. Student theses were excluded, as were conference abstracts, unpublished material, and two studies in which data on paternal and maternal occupational exposures were pooled. The relative risk of spontaneous abortion was estimated. RESULTS: One study found no increase in risk of abortion when gases were scavenged or when the exposure to unscavenged gases was low. None of the studies included ambient gas sampling. 24 comparisons between exposed and unexposed women, obtained from 19 reports, were included. The overall relative risk was 1.48 (95% confidence interval (95% CI), 1.4 to 1.58). To test whether this result was influenced by the quality of the studies, the validity of the reviewed papers was rated on the basis of three criteria: appropriateness of the unexposed comparison group, control for non-occupational confounding variables, and response rate. The estimate of risk increased to 1.9 (95% CI, 1.72 to 2.09) when analysis was restricted to the six comparisons which were rated the most rigorous. CONCLUSIONS: Epidemiological studies based on data obtained in the prescavenging era indicate an increased risk of spontaneous abortion. The estimated increased risk was not diminished but rather increased by exclusion of the more methodologically flawed studies.
Từ khóa
Tài liệu tham khảo
Cohen et al 1971" 36 Operating room nurses
'9 Rosenberg and Kirves 197323 Cohen 1974
Nurse anaesthetists
Physicians, anaesthesia Cohen et al 19806 400 Dental assistants, high exposure Lauwerys et al 259 Operating room physicians, 1981
"5 workers, high exposure Heidam 1984'8 179 Dental assistants, private clinics, N20
Time window for Inclusion of Occurrence of pregnancies exposure Hemminki et al 1985"2 169 cases; 469 controls Nurses
Similar occupations (score=l). We included here: operating room nurses versus other nurses,"'6172425 anaesthetists versus other physicians," exposed versus unexposed anaesthetists,' exposed versus unexposed nurse anaesthetists,' exposed versus unexposed operating room nurses or technicians,' and exposed versus unexposed hospital workers.9 We see that in some of these studies, the employment status of the unexposed women was unclear or unspecified.
Dissimilar occupations (score=O). We included here: exposed workers compared with women in any other activity, including no work.'5 19-21 Any study which explicitly included unemployed women in the unexposed group received a score of 0.
Non-occupational variables may also act as confounding factors in these studies. Risk of spontaneous abortion is reported to increase with increasing maternal age,29 with smoking,'0" with alcohol consumption,'0 with use of coffee,30 and in one study, the odds ratios for the association between exposure to anaesthetic gases and spontaneous abortion were slightly lower when adjustment was made for radiation exposure.8
Control for one confounding variable (score= 1). All studies receiving a score of 1 controlled for maternal age.
No control for confounding (score=O).
Ericson and Kallen 1985'7