The aim of this methodological study was to validate a newly designed self-completion questionnaire assessing various dimensions of physical activity among 100 pregnant women in Bristol, UK. For this purpose different measures obtained by self-completion questionnaire were compared with those simultaneously obtained by two established assessment methods for physical exertion. Based on the findings it was suggested that the self-completion questionnaire be slightly modified by adding questions pertaining to household activities and deleting questions which proved to be conceptually meaningless. It is concluded that in future studies this strategy will facilitate the understanding of the complex relationship between way of life and pregnancy outcome.