Bibian van der Voorn

71 MEASUREMENT OF HUMAN MILK GC LEVELS Furthermore, maternal, perinatal stress experienced in the first days postpartum could have caused higher milk cortisol concentrations. However, in relation to reported cortisol concentrations in other studies who used immunoassays with 2 or without 4,5 enzymatic deconjugation and studies who used samples collected during the first days postpartum 5,7 the extremely high concentrations (~1700 nmol/L) reported by Groer et al. 6 cannot be explained. In conclusion, in this study we present a reliable LC-MS/MS method to measure cortisol and cortisone in human milk, using a relatively easy sample work-up which requires only a small amount of milk. Moreover, we showed that cortisol and cortisone in human milk are stable during 36h of storage at room temperature and during at least six freeze-thaw cycles. In addition, an overview of human milk cortisol and cortisone concentrations reported in literature is presented.