Objective: Self-efficacy has been shown to influence initiating and maintaining physical activity. Pregnancy often leads to a decline in physical activity and exercise self-efficacy assessments could be a tool to help women stay active during pregnancy. The Pregnancy Exercise Self-Efficacy Scale (P-ESES) is an English questionnaire assessing the self-efficacy in pregnant women to perform physical activity. The aim of this study was to translate the P-ESES questionnaire into a valid and reliable Danish version, P-ESES-DK.

Study design: The study included a qualitative design for the validation of the questionnaire and a prospective longitudinal observational study for the reliability testing.

Main outcome measures: The questionnaire was translated into Danish in a four-stage process with translation, back-translation and synthesis. The pre-final version was tested by eight women and changes were made to complete the final version of P-ESES-DK. The reliability testing was performed using a test-retest analysis of PESES-DK with 75 Danish pregnant women. Reliability was assessed using Intraclass Correlation Coefficient (ICC), Cronbach's alpha and agreement was visualized using a Bland-Altman plot.

Results: The questionnaire was found to have a good content validity. The assessment of the test re-test reliability showed an ICC of 0.809 and a Cronbach's alpha of the test and re-test were 0.839 and 0.869, respectively. The Bland-Altman plot showed that 93.9% of the answers were within the 95% limits of agreement.

Conclusions: The Danish version of P-ESES was found to be both reliable and valid. Thus, it can be used as a helpful tool to measure self-efficacy related to physical activity during pregnancy.