Night Work During Pregnancy and Preterm Birth-Register Study
Summary
This large Danish cohort study followed 16,501 pregnant women to test whether night-shift work increased the risk of preterm birth. Using detailed payroll records, researchers examined timing (first vs. second trimester), intensity (number and duration of night shifts), and patterns (consecutive nights, quick returns). Across all measures, night work was not linked to a higher risk of preterm birth compared to day-only work. Even women with frequent or consecutive night shifts showed no increased risk. A weak, non-significant increase was seen in women who switched from night work in the first trimester to day-only schedules in the second trimester, but overall results supported no association.
Why It Matters For Night Shift Workers and Night Owls
For pregnant workers, this study offers some reassurance: night shifts alone were possibly not tied to preterm birth risk. Unlike some smaller or self-reported studies, this research used precise registry data and looked at multiple aspects of scheduling, finding no harmful patterns. While pregnancy still requires careful monitoring, these results suggest that night work by itself may not be as risky for preterm delivery as once thought. This highlights the importance of using high-quality data when shaping workplace policies and provides a more evidence-based foundation for scheduling decisions during pregnancy.
Notes
Includes discussion of exposure misclassification issues.