Background Although working activities are associated with several pregnancy outcomes, there is scarce information regarding the association between working activities and low back pain (LBP) during pregnancy. This study aimed to investigate whether leisure-time and work-related physical activities during pregnancy are associated with LBP. Methods Data from the 2015 Pelotas Birth Cohort study were used. Demographic, socioeconomic, gestational, leisure-time (prior to and during pregnancy) and

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... k-related (days of work, hours of work, standing and heavy lifting) physical activity data were collected at birth. LPB was assessed in the 12-month follow-up period. Results Leisure-time physical activity either prior to and during pregnancy was not associated with LBP. Working during pregnancy, days of work and standing position at work were not associated with self-reported LBP during pregnancy. However, working more than 8 h per day and always lifting heavy objects at work increased the odds ratio for LBP (OR 1.30 95%CI: 1.04; 1.63; and OR: 1.39 95%CI 1.08; 1.81, respectively). In addition, women who had lifted heavy objects often/always, reported an increase in pain intensity. Conclusion Working during pregnancy and days worked per week were not related to experiencing LBP. However, women who worked more than 8 h per day, as well as women who lifted heavy objects at work on a regular basis, were more likely to experience pregnancy-related LBP.