Resumen
Background: Becoming a parent may cohere with drastic changes in physical activity (PA) and sedentary behavior (SB). A clear understanding of determinants of changes in PA and SB during pregnancy and postpartum is needed to facilitate the development of tailored family-based interventions. Methods: Thirteen focus group discussions targeting determinants of changes in PA and SB behavior were conducted, involving a total of 74 expecting and first-time parents. A semi-structured question guide was used to facilitate the discussions. Results: Four main levels of determinants were identified: the individual (including psychological, situational and biological determinants), interpersonal, environmental and policy level. Some determinants were mentioned to be a barrier (e.g., ?barriers to self-care?) while others were a facilitator (e.g., ?weight control?). Determinants were related to both PA and SB and applicable during pregnancy as well as postpartum (e.g., ?self-regulation?), or only related to one behavior and/or one period (e.g., ?feeding baby?). Some were described by both parents (e.g., ?parenthood perceptions?), whereas others were mentioned by women (e.g., ?PA knowledge?) or men (e.g., ?time opportunities?) only. Conclusions: Focus should be given to interventions aimed at improving parents? self-regulation skills and support on how to cope with interpersonal and situational constraints as well as parenthood perceptions.