Norlén F, et al. - In this prospective national cohort study, researchers examined the association between occupational exposure to inorganic particles or welding fumes during pregnancy and negative birth results. The study sample consisted of all single births by occupationally active mothers (995,843). According to results, mothers who were highly exposed to inorganic particles and had less than 50 days off work during pregnancy showed an increased risk of premature birth, low birth weight and small for gestational age. The increased risks have been driven by iron particle exposure. There were no increased risks associated with stone and concrete particle exposure. Findings suggested an association of high exposure to welding fumes with an increased risk of low birth weight and preterm birth. Overall, the investigators recommended that women who are pregnant should not be exposed to high iron particle levels or welding fumes.