The Relationship of Preterm, Term, and Post-Term Births to Maternal Stress and Human Milk Cortisol Levels.

Maternal stress can lead to changes in the composition of human breast milk. The present study evaluates cortisol levels in the breast milk of mothers after giving birth preterm, term, or post-term, and ascertains whether the levels are associated with maternal stress. Included in the study were mothers who gave birth vaginally after 32 weeks of gestation between January and April 2022. The breast milk was expressed with an electronic pump under the supervision of a nurse on day 7 following birth, and 2 mL samples of the milk were transferred into microtubes and stored at -80°C. Stress in the mothers was measured using the perceived stress scale developed by Cohen et al. The human breast milk cortisol levels were determined using an enzyme-linked immunoassay in a single session. A total of 90 mothers, including 30 with preterm births, 38 with term births, and 22 with post-term births, were included in the study. The median stress scale score was 28 (17-50) and the median breast milk cortisol level was 0.49 ng/mL (0.1-1.96 ng/mL). A significant positive correlation was noted between the stress scale scores and breast milk cortisol levels ( = 0.56,  < 0.01). The breast milk cortisol levels and maternal stress scale scores were significantly higher in the preterm birth group than in the term birth group ( = 0.011 and  = 0.013, respectively). Although there is an association between maternal stress and preterm labor and milk cortisol levels, we believe that more studies are needed to establish a causal link.