As more women join the skilled-trade workforce, the effects of workplace exposures on pregnancy need to be explored. This study aims to identify the effects of mild steel and stainless steel welding fume exposures on cultured placental trophoblast cells.Welding fumes (mild steel and stainless steel) were generously donated by Lincoln Electric. Electron microscopy was used to characterize welding fume particle size and the ability of particles to enter extravillous trophoblast cells (HTR-8/SVneo). Cellular viability, free radical production, cytokine production, and ability of cells to maintain invasive properties were analyzed, respectively, by WST-1, electron paramagnetic resonance, DCFH-DA, V-plex MULTI-SPOT assay system, and a matrix gel invasion assay.For all three welding fume types, average particle size was < 210 nm. HTR-8/SVneo cells internalized welding particles, and nuclear condensation was observed. Cellular viability was significantly decreased at the high dose of 100 µg/ml for all three welding fumes, and stainless steel generated the greatest production of the hydroxyl radical, and intracellular reactive oxygen species. Production of the cytokines IL-1β and TNFα were not observed in response to welding fume exposure, but IL-6 and IL-8 were. Finally, the invasive capability of cells was decreased upon exposure to both mild steel and stainless steel welding fumes.Welding fumes are cytotoxic to extravillous trophoblasts, as is evident by the production of free radicals, pro-inflammatory cytokines, and the observed decrease in invasive capabilities.