Objectives The influence of occupational physical activity on pregnancy duration and birthweight was examined.

Methods In this prospective study information on levels of occupational physical activity was collected during a personal interview before pregnancy, and possible changes were registered during follow-up, which lasted until after birth. Data on pregnancy duration and birthweight were obtained from midwives, physicians, and obstetricians. The occupational energy expenditure was operationalized in intensity and fatigue scores, which were studied as such and in combination with workhours and work speed. The occupational biomechanical load was operationalized in a peak and a chronic pressure score.

Results Participants were part of a group of 260 cleaners, kitchen staff, and clerical workers enrolled from 39 Dutch hospitals between August 1987 and January 1989 before they became pregnant. One hundred and twenty-eight of these women were eligible for study because they became pregnant, they worked at least six weeks during pregnancy, and information on work aspects during pregnancy and pregnancy outcome was complete. Work with a high intensity score, and to a less extent work with a high fatigue score, had the most outstanding effect (up to 18 d shorter) on the pregnancy duration when the work speed was high. None of the studied aspects of occupational physical activity showed a relevant influence on birthweight when adjusted for pregnancy duration.

Conclusion This study indicates that the levels of occupational physical load found in the work of nonmedical hospital staff, especially when combined with high work speed, can lead to a shorter pregnancy period.

Key terms biochemical load; cleaner; clerical worker; energy expenditure; kitchen staff