"Occupational studies included in this review found that several occupational and non-occupational factors influenced reproductive outcomes. Occupational factors involved included standing, lifting, and exposure to chemicals—typically, individuals exposed to noise were also exposed to other occupational hazards. Important non-occupational factors were mother’s age, mother's weight and height, mother’s weight gain during pregnancy, smoking, education, race and socioeconomic status. Gravidity and parity, and chronic diseases of the mother were also important factors for the examination of spontaneous abortion or preterm labour."