The purpose of this systematic review was to explore whether birth weight, early growth and motor development act as determinants of physical activity in children and youth. Methods: We performed a systematic literature search on the possible early life determinants. A meta-analysis was performed on the association between birthweight and objectively measured physical activity. Results: We identified 9 studies examining birth weight, in which none of the studies with objectively measured physical activity observed an association between birth weight and physical activity. The meta-analysis confirmed this result (b=-3.08, 95% CI -10.20, 4.04). The 3 studies examining early growth and physical activity in youth differ in methodology and the results are inconsistent. Two studies suggest an association between earlier motor development and physical activity and sport participation in youth. This was not confirmed in a third study. Conclusion: Our meta-analysis suggests that birth weight is not an important determinant of physical activity in youth. Available data does not allow firm conclusions whether early growth and motor development act as determinants of physical activity in youth.