The aim of this study was to evaluate the impact of type of employment and level of physical activity at work on the risk of severe preeclampsia. For this purpose, we carried out a case control study of 160 nulliparous pregnant women with severe preeclampsia and 320 normotensive nulliparous controls who received prenatal care from members of one medical staff. The type of employment and the level of physical activity sustained at work were ascertained at birth through an interview based on a standard questionnaire. The degree of physical activity at work was assessed by a 4-level activity score based on type of work, physical intensity, posture at work, and weekly working hours. In logistic regression analysis, after adjustment for potential confounders (maternal age, time of stopping work, prepregnancy body mass index, social status of the partner, history of previous abortion, and prepregnancy smoking status), clerical workers had a significantly lower risk of severe preeclampsia than women who were unemployed at the beginning of pregnancy (OR 0.53, 95% CI 0.30, 0.96). In multivariate analysis, there was a significant linear trend relating the degree of physical activity at work, to the risk of preeclampsia (likelihood chi-square = 9.38, 3 df, p = 0.002). We then restricted the analysis to women who had ever worked in pregnancy (n = 339) also adjusting for confounders, and found that clerical workers were still at significantly lower risk of severe preeclampsia than women not formally employed (OR 0.2, 95% CI 0.08, 0.49). In addition, moderate/high physical activity at work was associated with a 2-fold increase in the risk of severe preeclampsia compared to mild activity (OR 2.08, 95% CI 1.11, 3.88). We conclude that moderate to high physical activity at work seems to increase the risk of severe preeclampsia.