Overall , mean ( SD ) maternal ( range : 81.2 20.4 to 86.2 19.9 g/L ) and infant ( 55.6 16.3 to 61.0 15.4 g/L ) plasma selenium concentrations increased , whereas breast-milk selenium concentrations declined ( 14.3 11.5 to 9.8 7.3 g/L ) from 2 or 6 to 24 wk postpartum ( all P < 0.001 ) .