- We examined the relationship between occupation and clinical characteristics during pregnancy and medical recommendations to stop working. Using a case-control design, we compared 58 working women who had preterm births, with 126 who had delivered at term. All women were interviewed postpartum while still in hospital. There were no differences between the groups with regard to physical activity outside the home, weekly work hours, nor duration of work. Only a small proportion had been exposed to unusually difficult working conditions, to hazardous agents or to a very uncomfortable working environment. Women who had had preterm births were advised more often to leave their jobs or modify their working patterns. Multivariate analysis revealed that the physician's decision to recommend cessation of work was influenced primarily by complications during the current pregnancy. It appears that our patients at risk for preterm birth are probably correctly identified, and receive appropriate guidelines as to working patterns. It is possible that a poor obstetric history or previous abortions may paradoxically have a protective effect, as they influence the physician to recommend cessation of work.