Background: Preterm birth is a stressful event for both the mother and infant. Whereas the initiation of breastfeeding is important for preterm infant health, little is known of the glucocorticoid hormones (cortisol and cortisone) in human milk following preterm birth. Research aim: The aim of this study was to investigate the relationship between human milk glucocorticoid concentrations and preterm birth.
Methods: Human milk was sampled weekly for up to 6 weeks from 22 women who delivered a preterm infant at 28 to 32 weeks' gestation. Human milk was analyzed for total and free cortisol and cortisone concentrations using liquid chromatography-tandem mass spectrometry.
Results: Milk sampled from mothers of preterm infants had more cortisone than cortisol ( p < .001), with a strong correlation between both hormones ( p = .001, r = .85). The cortisone was significantly higher in the milk of mothers who delivered infants after 30 weeks compared with those who delivered before 30 weeks of gestation ( p = .02). Glucocorticoid concentrations did not change over the sampling time (weeks 1 to 6 postpartum) and did not differ by infant gender.
Conclusion: Glucocorticoids were present in all milk samples following preterm birth. Cortisone concentration tended to be higher in those who delivered after 30 weeks' gestation but did not increase further over the weeks following birth.
Keywords: breastfeeding; hormones; human milk; maternal health; prematurity.