Background Due to health effects from participating in physical activity (PA) it is from a public health perspective important to study how participation PA may change over a lifetime and how different life events impact on the participation. Although studies in the field are sparse, parenthood has been found to be a life event associated with decreased PA, especially among women. We studied physical activities performed among women and men with and without children. Methods This study includes data for from parents-to-be, 224 women and 208 men, from Karlskrona municipality, situated in the south eastern part of Sweden. Data collection was carried out during 2008–2009. When contacting the antenatal clinics in the municipality all expectant parents were asked by the midwife about participation in the study. Respondents completed a questionnaire about age, socioeconomic status, level of education, previous children, smoking and alcohol habits, Body Mass Index, self estimated health, and participation in different kinds of outdoor and indoor recreational PA. We measured the self-reported amount of outdoor recreational PA undertaken during the last year. Results Both women and men without children performed more outdoor and indoor PA compared to those who had children. Women walked significantly more (p = 0.017) than men irrespective of whether or not they had children. Women with children participated in significantly more gardening (p = 0.009) and winter sports (p = 0.013) than women without children, and women without children participated in significantly more PA indoors (p = 0.001) than women with children. Men with children participated in significantly more gardening (p = 0.001) than men without children, and men without children participated in significantly more PA indoors (p = 0.006). Conclusions Becoming a parent is a life event that affects participation in PA, both concerning duration and the kind of activities performed. To gain deeper understanding and more insight about reasons for these changed patterns of PA as well as the effects on the outcome of the parents health in a short- and long term would be important to follow prospectively.