GSTM1 and anemia: Per IQR increase of SO42− at lag01 month decreased the Hb concentration (β: − 0.38, 95% CI: − 0.75, − 0.01, g/L) and per IQR increase of SO42− at lag01, lag02, and lag03 months increased the risk of anemia (OR: 1.09–1.10) in multiparous pregnant women, while lag effects of PM2.5, BC, NH4+, NO3−, OM, and Dust on Hb and anemia were not identified in other lag models for multiparous pregnant women.