Statistical analysis
REGRESSION, SECONDARY
A retrospective sample size calculation performed for the prespecified secondary outcome, GWG, showed an estimated sample size of 33 participants in CON and 66 participants in each intervention group to detect a difference of 2.8 kg between CON and the intervention groups (statistical analysis plan available with trial registration at clinicaltrials.gov). Data are presented as mean ± standard deviation (SD) for approximately symmetric distributions, median and interquartile range (IQR) for asymmetric distributions, and frequency and proportion for categorical data. Estimated effect sizes are presented with 95% confidence interval [95% CI]. Statistical analyses were performed using R [Analysis of GWG was based on the intention-to-treat principle including all randomized participants. Trajectories of observed gestational weights during pregnancy were modelled by a mixed effects model featuring an intercept constrained to be equal across groups due to the randomized design [We used the randomized controlled trial design to investigate differences between groups in GWG and obstetric and neonatal outcomes, and an observational design combining all participants independent of group allocation to investigate associations between prenatal physical activity measures per se and GWG. Between-group comparisons of estimated GWG after each trimester were performed using analysis of variance (ANOVA). A sensitivity analysis was conducted using linear regression to investigate total GWG in each group before and during COVID-19, where the intervention groups received in-person and online interventions, respectively. Another sensitivity analysis using ANOVA included only participants, whose weight were measured at the hospital, to investigate the influence of weight measurements being obtained by the calibrated scale at the hospital versus via the participants’ home scales. For obstetric and neonatal outcomes, differences between groups were tested with Pearson’s χAssociations between physical activity measures and total GWG among all participants were performed using linear regression. Physical activity measures (moderate-to-vigorous-intensity physical activity (min per week), steps (per day), and active kilocalories (per day)) used for association analyses were the average values from randomization to delivery day for participants who delivered at GA ≤ 40 + 0 weeks, and from randomization to GA 40 + 0 weeks for participants who were lost to follow-up before delivery or delivered at GA > 40 + 0 weeks.