Research from Perth's Telethon Institute for Child Health Research has found a link between the number of stressful events experienced during pregnancy and increased risk of behavioural problems in children.
The study has just been published online in the latest edition of the top international journal Development and Psychopathology.
Common stressful events included financial and relationship problems, difficult pregnancy, job loss and issues with other children and major life stressors were events such as a death in the family.
Lead author, Registered Psychologist Dr Monique Robinson, said while previous studies have shown a link between stress and poorer outcomes, this study goes further by analysing the timing, amount and kinds of events that lead to poorer outcomes.
"What we have found is that it is the overall number of stresses that is most related to child behaviour outcomes," Dr Robinson said. "Two or fewer stresses during pregnancy are not associated with poor child behavioural development, but as the number of stresses increase to three or more, then the risks of more difficult child behaviour increase."
Dr Robinson said the actual type of stress experienced was of less importance than the number of stresses, and there was no specific risk associated with the timing of these stress events - early or late - in the pregnancy.
The analysis was undertaken on data from Western Australia's long-term cohort Raine Study, which recruited nearly 3000 pregnant women and recorded life stress events experienced at 18 and 34 weeks of pregnancy, as well as collecting sociodemographic data. The mother's experience of life stress events and child behavioural assessments were also recorded when the children were followed-up ages 2, 5, 8, 10, and 14 years using a questionnaire called the Child Behaviour Checklist.
The percentage of women with more than two stress events was 37.2%, while the percentage with six or more was 7.6%.
Dr Robinson said the study should not make pregnant women stress further about the stress in their lives.
"These types of analyses look at overall population risk, and of course individuals can have very differing responses," Dr Robinson said.
"Regardless of exposure to stress in the womb, a nurturing environment after birth can provide the child with enormous potential to change their course of development. This is known as "developmental plasticity", which means that the brain can adapt and change as the child grows with a positive environment.
"The important message here is in how we as a community support pregnant women. If we think about people who lead stressful lives, they are most often linked with socioeconomic disadvantage. This research shows we should be targeting these women with support programs to ensure the stress does not negatively affect the unborn child."
Dr Robinson said further research is needed to understand the mechanisms behind how stress in pregnancy affects the developing baby, including the impact of maternal stress hormones, attachment and parenting issues and socioeconomic factors.