Objectives Pregnancy represents a dynamic period when both work conditions and worker assessment of occupational psychosocial stressors may change. We undertook longitudinal repeated measurements of job control, efforts, reward, and overcommitment in pregnant working women to assess direction and magnitude of change across pregnancy.

Method The Job Content and Effort-Reward Imbalance (ERI) Questionnaires were given to 61 working pregnant women recruited at 8–12 weeks gestation and repeated 3 more times across the pregnancy. Demographic data, self-rated (SR) health and stress measures, and blood pressure (BP) data were also collected at each visit. Results were analysed using multilevel linear regression models and generalised estimating equations.

Results 56 subjects (91%) completed at least two waves; 42 (69%) completed all four. Progressive declines in job efforts, rewards, and overcommitment were noted across pregnancy; ERI remained stable. Job Control increased. Black subjects showed evidence of lower job control but also lower effort-reward imbalance across pregnancy, contrasted with Whites/Hispanics. Overcommitment showed the strongest negative association with indices of maternal health, including BP, and SR stress and health. The strongest associations of job constructs with maternal health were noted at mid-second trimester (20–24 weeks) with a decline thereafter.

Conclusions Correlations between occupational psychosocial stressors and intermediate pregnancy-related outcome variables are greatest in early-to-mid-pregnancy. Declining effort and increased control across pregnancy suggest that, in this group, work conditions may be improved, either by the employer or worker, as pregnancy progresses. The possibility of a critical period when associations between work stressors and pregnancy outcomes is also suggested by these results.