Background Increased stress levels at work may be associated with adverse effects on pregnancy outcomes, but studies have been inconclusive so far. Therefore, we aimed to investigate the effects of maternal exposure to work-related stress during pregnancy on birth weight and gestational age.

Methods The study was conducted among women participating in the PRegnancy and Infant DEvelopment (PRIDE) Study, a nationwide prospective cohort study in the Netherlands which follows women and their offspring from early pregnancy onwards using repeated web-based questionnaires. The level of work-related stress was assessed in gestational week 17 by a validated Dutch version of the Job Content Questionnaire, comprising questions on job demands (work pace, psychological demands, and physical demands) and job control. Based on summary scores, participants were classified as having low (<50%), moderate (50–90%), or high (>90%) job demands and low (>90%), moderate (50–90%), or high (<50%) levels of control. High job strain was defined as the combination of high job demands and low or moderate levels of control. Confounding-adjusted effect estimates for associations between these exposures and the outcome parameters low birth weight (<2500 grams) and preterm birth (<37 weeks of gestation) were calculated using logistic regression analyses.

Results In total, 1165 out of 1369 women with a singleton pregnancy resulting in a live birth before May 1st 2015 were included in the analyses. High total job demands and high job strain seemed to increase the risk of delivering a low birth weight infant (OR = 3.1, 95% CI: 0.9–11.3 and OR = 3.3, 95% CI: 0.9–12.1, respectively). Moderate or high levels of job control were associated with a reduced risk of preterm birth (OR = 0.5, 95% CI: 0.3–1.1).

Conclusion This study showed that exposure to work-related stress may have adverse effects on birth weight, whereas more job control seems to reduce the risk of preterm birth.