Physical activity significantly impacts public health as it reduces the risk of chronic diseases and provides numerous protective factors during pregnancy. Although Canadian guidelines recommend regular physical activity for healthy pregnant women, little is known about their leisure-time physical activity patterns. This study compared the physical activity levels of pregnant and non-pregnant women and examined socio-demographic and health correlates of physical activity during pregnancy. Canadian Community Health Survey data (2005-2008) from 623 pregnant women and 20,392 non-pregnant women aged 15-49 years in Ontario, Canada were examined. The prevalence of regular physical activity (15 or more minutes on at least 3 days of the week) was 58.3 % [95 % CI 52.9, 63.4], among pregnant women and 66.9 % [95 % CI 65.8, 68.0] among non-pregnant women. However, the prevalence of meeting Canadian guidelines for physical activity during pregnancy (30 or more minutes on at least 4 days of the week) was only 23.3 %, [95 % CI 19.4, 27.7] among pregnant women and 33.6 % [95 % CI 32.7, 34.6] among non-pregnant women. Pregnant women were less likely to be meeting guidelines if they were single, divorced, separated or widowed, a visible minority, had a household income between $20,000 and $79,999, and reported being in good or fair/poor health; when it came to education, women who had completed high school were more likely to be meeting guidelines. Few pregnant women in Ontario are meeting guidelines for physical activity during pregnancy. Results indicate that promoting physical activity during pregnancy should remain a public health priority.