Shift work, job stress, and late fetal loss: The National Birth Cohort in Denmark.

Objective: The Danish National Birth Cohort (DNBC) was used to examine whether shift work or job stress correlate with late fetal loss. Methods: We identified 33,694 pregnancies of daytime workers and 8,075 pregnancies of shift workers in women recruited to the DNBC between 1998 and 2001. Pregnancy outcomes were obtained by linkages to the national registers. Hazard ratios of fetal loss were calculated by using Cox regressions with left truncation. Results: Fixed night work was associated with fetal loss (hazard ratio = 1.85, 95% confidence interval = 1.00-3.42). No high risk of fetal loss was seen for other types of shift work. Job stress, as measured in our study, was not associated with fetal loss. Conclusions: Our results suggest that fixed night work during pregnancy increases the risk of late fetal loss.