Shift work, nitrous oxide exposure, and spontaneous abortion among Swedish midwives.
OBJECTIVE
To study the relation between irregular work hours, nitrous oxide (N2O) exposure, and the risk of spontaneous abortion.


METHODS
All 3985 female members of the Swedish Midwives Association in 1989, born in 1940 or later, received a questionnaire on exposure before and during all of their pregnancies. Questions on work conditions covered occupation, extent of employment, workplace, work schedules, use of anaesthetics, and work load. The association between exposure variables and spontaneous abortion was analysed by logistic regression models.


RESULTS
Night work and three shift schedules among midwives showed increased odds ratios (ORs) (95% confidence intervals (95% CI)) 1.63 (0.95-2.81) and 1.49 (0.86-2.59), respectively. The ORs of late spontaneous abortions (after the 12th week of pregnancy) was increased for night work 3.33 (1.13-9.87). Use of N2O (> 50% of the deliveries) was not associated with increased risk of spontaneous abortion OR 0.95 (0.62-1.47). Frequent or permanent shortage of staff was related to an increased risk of spontaneous abortions before the 13th week of pregnancy.


CONCLUSIONS
The results support the hypothesis that night work and high work load increase the risk of spontaneous abortion.
Axelsson
G
G
Department of Environmental Medicine, Göteborg University, Sweden.
Ahlborg
G
G
Bodin
L
L
D000022:Abortion, Spontaneous / Q000139:chemically induced*; D000328:Adult; D005260:Female; D006801:Humans; D008875:Middle Aged; D008880:Midwifery; D009609:Nitrous Oxide / Q000008:administration & dosage / Q000009:adverse effects*; D009784:Occupational Diseases / Q000139:chemically induced*; D016273:Occupational Exposure / Q000009:adverse effects*; D010561:Personnel Staffing and Scheduling; D011247:Pregnancy; D012307:Risk Factors; D013548:Sweden; D016526:Workload
D009609:Nitrous Oxide