Maternal Prenatal and Postnatal Stress and Infections in Infancy.

Aim: To study maternal stress as a possible risk factor for early infections in infants in a well-characterised, prospective infant HELMi cohort.

Methods: We measured maternal stress during the last trimester with questionnaires (4 items, scales 0-100) and breastmilk cortisol levels at 3 months. We compared maternal stress between infants with several infections (n = 125) and infants with no infections (n = 122) during the first 6 months of life. The episodes and days with symptoms were recorded using an online diary. Control subjects were matched for sex, year of birth, mode of delivery, and timing of breastmilk sample. The analysis was adjusted for season of birth and number of siblings.

Results: The median maternal prenatal stress, related to household during the last trimester, was higher in the infection group than in controls (37 [IQR 19.5-61] vs. 19 [7.8-42.3]; p = 0.02). There was no difference in prenatal stress related to pregnancy or the relationship between the groups. The breastmilk cortisol levels did not differ between the groups (medians of 6.8 nmol/L [IQR 4.8-8.8] and 6.2 nmol/L [4.5-8.4], respectively; p = 0.12).

Conclusion: Prenatal stress was linked to the occurrence of infections in infancy. Whether support for stress reduction may reduce the risk for infections warrants further study.