Seventeen mothers were enrolled in this study. Foremilk was obtained from three nipple openings on each breast. After the breastfeeding session, hindmilk was sampled in the same manner. We measured creamatocrit (CrCt) and analyzed the protein concentration. Data were analyzed with the paired t test and Wilcoxon signed-rank sum test where appropriate. Coefficient of variance (COV) was calculated to identify the variation of protein content among different mammary lobes.