Effect of maternal work shifts and household income on preterm birth: A nested case-control study

To assess how maternal work shifts impact preterm birth (PTB) onset and to evaluate the modifying effect of maternal household income on this association.

We analyzed a prospective cohort nested case-control sample, of all residents in Wuhan from 2011 to 2013. All births in the city-center districts were included, and a home-visit interview was conducted for all sampled births to collect data on factors such as maternal health, behaviors, and occupational and environmental exposures. Logistic regression models were developed to assess how maternal work shifts influence the onset of PTB, while controlling for potential confounders. The modifying effect of maternal household income was further evaluated through a stratified analysis. We tested result stability using sensitivity analyses.

Our study included 2393 PTBs and 4263 controls. Increased PTB risk was observed among women engaged in shift work (adjusted odds ratio [aOR] 1.19, 95% confidence interval [CI] 1.05-1.34), with this association being stronger among women whose monthly household income was below the median income level in the city (aOR 1.26, 95% CI 1.09-1.45).

Higher PTB risk was observed among pregnant women engaged in shift work, with those from lower-income households being more vulnerable to this effect. Future studies are needed to confirm these associations.