Sample Size Calculation Data from Pomeroy et al.in 2012 stated that when using an accelerometer to measure physical activity and air displacement plethysmography to measure neonatal body composition (the same measurements we are proposing to use), the Spearman correlation coefficient showing the association between maternal physical activity level and neonatal fat free mass is r=0.5226. Using this R-value and an alpha of 0.05, 30 total participants (15 per group) are needed to adequately power our study at .85 (beta=.15).