Body weight loss after birth increases stress in the newborns

Background: Body weight loss is physiological when is lower than 8–10% in the first days of life. Low birth body weight is correlated to up regulation of hypothalamus-pituitary-adrenal axis function. The aim was to test the hypothesis that weight loss from 24 to 48 h of life is associated with high levels of salivary cortisol in healthy term newborns. Methods: a prospective clinical study was performed enrolling healthy term newborns who started the rooming- in the delivery room to improve skin to skin and breastfeeding. Salivary cortisol levels were measured at 24 and 48 h of life, using Salimetrics Salivary Cortisol Enzyme Immunoassay Kit. Weight loss/gain was recorded every 24 h starting from birth. Results: A significant positive correlation was found between salivary cortisol levels and body weight loss at 48 h of life (n = 57, r = 0,393; p = 0,006). At 48 h of life, salivary cortisol levels were significantly higher in newborns that lost body weight 1,7 times more than body weight loss at 24 h of life compared to newborns who maintained a more stable body weight between 24 and 48 h of life Conclusions: The swift body weight loss from 24 to 48 h of life increases salivary cortisol levels in term newborns. Data suggest the need to protect exclusive breast fed newborns with human milk donor in term newborns, in case of temporary breast milk lack, to reduce cortisol exposure early in life