Background: Studies showed that many women probably don't engage in enough physical activity during pregnancy. Physical activity can greatly contribute to the well-being of both the mother and her baby. Objective: To estimate pregnant women's level of physical activity and its determinants. Methods: A cross-sectional study was conducted on pregnant females during the last trimester in Mansoura University Hospital, Gynecology, and Obstetric Department during the year 2022. Data were collected using a semi-structured questionnaire assessing physical activity in different situations including tasks related to managing a household and providing care, transportation activities and inactivity, sports activities and activities during work. Results: Total 386 pregnant females were included with average age 27.9±6.5 years. Approximately 38.6% were housewives, 42.0% employees, and 19.4% manual workers, 50.8% rural residents, and 31.6% university education or higher. Approximately 7.5% had gestational hypertension, 13% gestational diabetes, 35.8% anemia, 16.3% other comorbidity, and 3.4% smokers. Prevalence of insufficient physical activity assessed during out-of-work, going places, fun or exercise, at work, and overall was 87%, 87.6%, 89.6%, 92% & 95.6%, respectively. Approximately 58% self-rated physical activity before pregnancy as insufficient. Multivariate analysis showed that cesarean delivery, insufficient self-rated pre-pregnancy level of physical activity, absence of hypertension during pregnancy, increased body mass index are significant predictors of low to moderate overall physical activity. Conclusions: The study findings underscore the extremely high level of physical inactivity among pregnant females attending University Hospital in Egypt. There is urgent need for preventive and educational programs targeting pregnant women in their last trimester.