Changes in leisure-time physical activity among Brazilian pregnant women: comparison between two birth cohort studies (2004 – 2015)

BACKGROUND Low levels of leisure-time physical activity (LTPA) during pregnancy have been shown in studies conducted worldwide. Surveillance is extremely important to monitor the progress of physical activity patterns over time and set goals for effective interventions to decrease inactivity among pregnant women. The aim of this study was to evaluate time changes in LTPA among Brazilian pregnant women in an 11-year period (2004-2015) by comparing data from two birth cohort studies. METHODS Two population-based birth cohort studies were carried out in the city of Pelotas, southern Brazil, in 2004 and 2015. A total of 4244 and 4271 mothers were interviewed after delivery. Weekly frequency and duration of each session of LTPA in a typical week were reported for the pre-pregnancy period and for each trimester of pregnancy. Trends in both recommended LTPA (≥150 min/week) and any LTPA (regardless of weekly amount) were analysed overtime. Changes were also calculated separately for subgroups of maternal age, schooling, family income, parity, pre-pregnancy body mass index and pre-pregnancy LTPA. RESULTS The proportion of women engaged in recommended levels of LTPA pre-pregnancy increased from 11.2% (95%CI 10.0-12.2) in 2004 to 15.8% (95%CI 14.6-16.9) in 2015. During pregnancy, no changes were observed over the period for the first (10.6 to 10.9%) and second (8.7 to 7.9%) trimesters, whereas there was a decrease from 3.4% (95%CI 2.9-4.0) to 2.4% (95%CI 1.9-2.8) in the last trimester. Major decreases in LTPA in the last trimester were observed among women who were younger, with intermediate to high income, high schooling, primiparous, pre-pregnancy obese and, engaged in LTPA before pregnancy. Changes in any LTPA practice followed the same patterns described for recommended LTPA. CONCLUSIONS Despite the increase in the proportion of women engaged in LTPA before pregnancy between 2004 and 2005, LTPA levels remained stable during the first and second trimesters of pregnancy and declined during the third gestational trimester over the period. Interventions to encourage the maintenance of LTPA practice throughout pregnancy are urgently needed.