days among 21 lactating women in the United States and found no change in milk volume and no correlation between fluid intake and milk volume (Figure 5-4).
In an earlier study, Illingworth and Kilpatrick (1953) asked 104 lactating women to drink at least 2,880 ml of liquid per day (high-fluids group) and 106 control women to drink as much as desired. In the first 9 days post partum, actual fluid intake averaged approximately 3,200 ml/day in the high-fluids group and about 2,100 ml/day in the control group. Neither infant growth in the first month nor duration of breastfeeding differed between groups. Milk intake at a test feed on the eighth day post partum tended to be lower in the high-fluids group. The authors thus cautioned against drinking fluids in excess of natural thirst inclination. However, thirst may sometimes function too slowly to prevention dehydration among women with high fluid losses resulting from exercise or high ambient temperature (experienced by many women without air conditioning in the summer). Thus, careful attention to adequacy of fluid intake is warranted in such situations, but under most conditions there appears to be no justification for emphasizing high fluid intake as a way to improve milk production.