New Australian research has found that even minor, everyday stress during pregnancy possibly affects a developing foetus.
Researchers from the Telethon Institute for Child Health Research in Western Australia say stress has an affect on the brain of the growing foetus and can cause problem behaviour by the time the child reaches pre-school age.
According to the researchers the psychological effects of financial troubles and personal conflict may begin even before birth and lower-level stresses, such as pregnancy problems, bereavement, relationship difficulties, job loss, money worries or moving house, also have an affect.
Other research has provided evidence that the children of mothers who experienced extreme trauma during pregnancy are less well-adjusted but this new research suggests that even mild stress has its consequences.
The study led by Monique Robinson, questioned almost 3,000 women in mid and late pregnancy about whether they were experiencing any of 10 potential stresses, and later correlated their responses with their children's behaviour.
It was found that by age two years the likelihood that children would be disobedient and aggressive increased in proportion to the amount of stress their mother had experienced while pregnant and this link remained by the time the children reached age five, but was less pronounced.
Ms Robinson says the effects might be the result of stress hormones triggered in the mother entering the bloodstream of the child before birth and she suggests people need to develop greater sensitivity to pregnant women's needs.
Ms Robinson says pregnancy is often a time when there is a lot of pressure on women to do the right thing and inflexible notions abound on how pregnant women should behave, such as overly prescriptive dietary advice and this possibly creates an atmosphere of anxiety even for women whose social circumstances are good.
Experts say it is already recognised that stressful environments are bad for the infant's brain and the new research confirms that more attention needs to be paid antenatally.
The researchers say it is also possible that women who were stressed during pregnancy might be more susceptible to stress during their children's early years.