Breast feeding, bottle feeding, and maternal autonomic responses to stress.

OBJECTIVE The aim of this study was to examine the effects of breast feeding on autonomic nervous system (ANS) response to stressors. METHODS Sympathetic and parasympathetic activities were examined before, during, and after standard laboratory stressors in women who were either exclusively breast feeding (n=14) or nonexclusively breast feeding (n=14), and in non-postpartum controls (n=15). RESULTS Mothers who breast fed exclusively showed greater levels of parasympathetic cardiac modulation and slower heart rate (HR) throughout the session and less HR increase and preejection period (PEP) shortening to mental arithmetic (MA) than did nonexclusive breast feeders and controls. Nonexclusive breast-feeders showed greater electrodermal reactivity to, and greater differences in skin conductance response (SCR) frequency between baseline and recovery from cold pressor (CP) than did either exclusive breast-feeders or controls. Sympathetic activity was negatively related to the number of breast feedings and positively related to bottle feedings. CONCLUSION Breast feeding shifts maternal ANS balance toward relatively greater parasympathetic and lesser sympathetic activity; the opposite occurs with bottle feeding. The frequency of feeding also is a critical factor in determining breast feeding effects on maternal ANS function.