Seasonal variation in salivary cortisol but not symptoms of depression and trait anxiety in pregnant women undergoing an elective caesarean section

OBJECTIVES: Seasonal changes in mood and behaviour are commonly reported in the general population but considerably less is known regarding seasonality and pregnancy. This study investigated the relationship between seasons and depression and anxiety symptoms, salivary cortisol concentrations, custom birthweight centiles (CBWC) and placenta weight for pregnant women living in South Wales. METHODS: This study utilised data from the longitudinal Grown in Wales (GiW) cohort. Women were recruited at the presurgical elective caesarean section (ELCS) appointment, when they provided saliva samples and completed the Edinburgh Postnatal Depression Scale (EPDS) and trait subscale of the State-Trait Anxiety Inventory (STAI). Data on birthweight and placental weight was extracted from medical notes. Seasonal data was available for 316 participants. RESULTS: No association was identified between seasons and EPDS (p = .178), STAI scores (p = .544), CBWC (p = .683) or placental weight (p = .857). Significance was identified between seasons and salivary cortisol concentration (p<.001), with highest levels in autumn and winter. Adjusted linear regression identified spring (B=−.05, p=.007, 95% CI −.09, −.01) and summer (B=−.06, p = .001, 95% CI −09, −.02) compared to autumn, and spring (B=−.05, p=.009, 95% CI −.09, −.01) and summer (B=−.06, p=.002, 95% CI −.10, −.02) compared to winter to be associated with decreased cortisol concentrations. CONCLUSION: This study found no association between season and maternally-reported mental health symptoms, birthweight by CBWC or placental weight but did between season and term salivary cortisol. This finding will have implications for studies that do not account for seasonality when using salivary cortisol as a biomarker.