Babies born during winter are at higher risk of developing mental health disorders, new research from Cardiff University has found. The study revealed that levels of the stress hormone cortisol are higher in women who give birth in autumn and winter compared to those who give birth in spring or summer.
Professor Ros John explained that cortisol levels naturally rise during pregnancy, but the data shows that autumn and winter babies are exposed to particularly high levels just before birth. On average, women giving birth in autumn or winter had 20% more salivary cortisol just before delivery than those giving birth in spring or summer.
Higher cortisol levels in pregnant women have previously been linked to a higher risk of children developing mental health disorders. The new findings could explain why these disorders are more common in people born during the winter months. However, the reason why women who give birth in winter or autumn have higher cortisol levels remains unclear.
The study involved 316 pregnant women in south Wales, with data gathered at pre-surgical appointments and immediately after birth through questionnaires and midwife notes. The research found a link between season and cortisol concentrations at term, though it did not explore the underlying cause of the seasonal variation.
