Limited association between markers of stress during pregnancy and fetal growth in “Born into Life”, a new prospective birth cohort

AIMS: We aimed to investigate the associations between perceived maternal stress or salivary cortisol levels during pregnancy and birth weight. METHODS: In 2010-2012 we recruited 92 women living in Stockholm, Sweden, and followed them from before conception and through pregnancy and childbirth. Their Perceived Stress Scale (PSS) scores and salivary cortisol levels were collected at 26-28 gestational weeks. Birth weight was collected from medical records. Linear regression analyses and Pearson correlations were performed between the PSS scores or cortisol levels and birth weight respectively, adjusted for gestational age. RESULTS: No significant associations were found between PSS scores or cortisol levels and birth weight. There was a trend towards higher salivary cortisol levels among infants with lower birth weights and this effect was attenuated after adjusting for gestational age. Morning cortisol levels (r=-0.31, p=0.01), the decline in cortisol levels (r=-0.26, p=0.03) and evening cortisol levels (r=-0.21, p=0.09) were negatively correlated with PSS scores. CONCLUSION: Maternal stress during pregnancy was not associated to birth weight. The inverse correlation between PSS scores and cortisol levels may indicate other mechanisms for maternal stress on child outcomes than the previous explanation of hypothalamic-pituitary-adrenal axis activity.Swedish Initiative for Research on Microdata in the Social and Medical Sciences (SIMSAM) framework grant no 340-2013-5867, as well as the Swedish Heart Lung Foundation, the Swedish Asthma and Allergy Association’s Research Foundation, grants provided by the Stockholm County Council (ALF project), FORTE, and the Strategic Research Program in Epidemiology at Karolinska Institutet.Accepte