Data: An increasing number of studies suggest that exposure to physically demanding work during pregnancy could be associated with increased risks of adverse pregnancy outcomes, but the results remain conflicted and inconclusive. The purpose of this study was to examine the influence of occupational activities during pregnancy on maternal and fetal health outcomes. Studies of all designs (except case studies and reviews) that contained information on the relevant population (women who engaged in paid work during pregnancy), occupational exposures (heavy lifting, prolonged standing, prolonged walking, prolonged bending, and heavy physical workload), comparator (no exposure to the listed physical work demands), and outcomes (preterm birth, low birthweight, small for gestational age, miscarriage, gestational hypertension, preeclampsia, gestational diabetes mellitus, stillbirth, and intrauterine growth restriction) were included. Five electronic databases and 3 gray literature sources were searched up to March 15, 2019. Eighty observational studies (N=853,149) were included. Low-to-very low certainty evidence revealed that lifting objects ≥11 kg was associated with an increased odds ratio of miscarriage (odds ratio, 1.31; 95% confidence interval, 1.08–1.58; I2=79%), and preeclampsia (odds ratio, 1.35; 95% confidence interval, 1.07–1.71; I2=0%). Lifting objects for a combined weight of ≥100 kg per day was associated with an increased odds of preterm delivery (odds ratio, 1.31; 95% confidence interval, 1.11–1.56; I2=0%) and having a low birthweight neonate (odds ratio, 2.08; 95% confidence interval, 1.06–4.11; I2=73%). Prolonged standing was associated with increased odds of preterm delivery (odds ratio, 1.11; 95% confidence interval, 1.02–1.22; I2=30%) and having a small-for-gestational-age neonate (odds ratio, 1.17; 95% confidence interval, 1.01–1.35; I2=41%). A heavy physical workload was associated with increased odds of preterm delivery (odds ratio, 1.23; 95% confidence interval, 1.07–1.41; I2=32%) and having a low birthweight neonate (odds ratio, 1.79; 95% confidence interval, 1.11–2.87; I2=87%). All other associations were not statistically significant. Dose-response analysis showed women stand for >2.5 hours per day (vs no standing) had a 10% increase in the odds of having a preterm delivery. Physically demanding work during pregnancy is associated with an increased risk of adverse pregnancy outcomes.