Experts warn that stress and depression are the major causes of babies arriving too early.
High levels of these hormones are involved in triggering labour, leading scientists to believe they could be behind many of the 45,000 premature births that occur in the UK each year – with potentially devastating results.
Premature babies – born before 37 weeks of pregnancy – are more likely to die in the first weeks of life and are at risk of a host of health problems, with one in ten developing a permanent disability such as lung disease, cerebral palsy, blindness or deafness.
While many of these early births can be explained by medical reasons, such as infection or complications with the pregnancy, around 30 per cent are unexplained.
Dr Veronica O’Keane, an expert in mental health in pregnancy, said “many thousands” of the unexplained premature births are likely to be caused by soaring levels of stress hormones – and they could be prevented by treating stress and depression in pregnancy.
Work carried out by Dr O’Keane, and presented at a London conference held by the Institute of Psychiatry, suggests that children whose mothers become depressed during pregnancy find it harder to handle stress themselves.
Tests on two-month-old babies showed that those whose mothers were depressed before their birth produced higher levels of stress hormones when given routine childhood jabs against infection.
It is thought that the hormones, including cortisol, play a key role in depression, meaning these children may be more prone to develop depression themselves in later life.
“This abnormality in cortisol secretion would seem to be an inter-generational way of transmitting depression without it being genetic,” said Dr O’Keane.
Sophie Corlett, of the mental health charity Mind, said that the stigma associated with depression meant that many pregnant women are reluctant to ask for help.
“When women are pregnant, they realise they are supposed to be full of excitement and they are bemused and slightly ashamed of not feeling that way, which can more difficult to seek support.”