ABSTRACT Introduction Physical activity (PA), regardless of domain, is recommended for pregnant individuals in clinical guidelines, but limited evidence is available for work-related PA. This study aimed to examine the associations of occupational (OPA) and leisure-time PA (LTPA) with plasma high-sensitivity C-reactive protein (hs-CRP), a risk marker for adverse pregnancy outcomes, among pregnant individuals. Methods This longitudinal study included 257 workers in the fetal growth cohort. OPA/LTPA and hs-CRP were measured in each trimester. OPA/LTPA was divided into high and low groups by the median level. Multivariable linear regressions were applied to estimate the adjusted geometric mean differences of hs-CRP (mg·L⁻¹) comparing high versus low OPA/LTPA in each trimester and the changes in OPA/LTPA over pregnancy. Results OPA was positively associated with hs-CRP (high: 5.14 vs low: 3.59; P value: 0.001) in the first trimester, particularly for standing/walking or walking fast, regardless of carrying things. LTPA was negatively associated with hs-CRP in the second (high: 3.93 vs low: 5.08; 0.02) and third trimesters (high: 3.30 vs low: 4.40; 0.046). Compared with the low OPA + high LTPA group, hs-CRP was higher in both the high OPA + high LTPA and high OPA + low LTPA groups in the first trimester, and in the high OPA + low LTPA group only in the third trimester. The change in OPA during pregnancy was positively associated with hs-CRP, whereas the change in LTPA was negatively associated with hs-CRP from the second to the third trimester. Conclusions In pregnant individuals, LTPA was negatively associated with hs-CRP, whereas OPA was positively associated with hs-CRP. More research on OPA’s health impact among pregnant individuals is needed, and guidelines may consider the potential unfavorable influence of OPA on pregnant individuals.