These findings, Dr. Petra Arck told Reuters Health in an email, could "allow clinicians to evaluate future asthma risk in unborn children using a simple life event assessment questionnaire."
Arck, of University Medical Center Hamburg-Eppendorf in Germany, and her colleagues note that although there are strong genetic components to asthma and related conditions, these alone do not help explain the unprecedented increase in such diseases in recent years.
Over the same period as that increase, they add, stress levels have been on the rise. But there hasn't been much evidence to connect stress in pregnancy to asthma and eczema.
To investigate further, the researchers examined data from 1,587 children and their mothers who took part in an Australian pregnancy study. The original purpose of the study was to determine the effects of intensive fetal monitoring on pregnancy outcomes.
Mothers-to-be were asked about recent stressful life events halfway through their pregnancy and again toward the end of pregnancy. Their children were evaluated for asthma, eczema and other allergy-related conditions at age six and 14.
Complete data were available for 994 children and their mothers.
The researchers calculated that the likelihood of having asthma or eczema as a teenager was substantially higher among children of mothers who experienced stressful life events during the second half of their pregnancies.
Specifically, kids were about twice as likely to have asthma as 14-year-olds if their mothers had been through a single stressful life event, once other factors known to influence asthma were taken into account. Risks were similar when mothers had experienced multiple life stressors.
When the researchers looked closer, they found that pattern only held among children whose mothers did not have asthma themselves.
There was no link between stressful events in pregnancy and a child's chance of having asthma or eczema at age six, according to findings published in the Journal of Allergy and Clinical Immunology.
The authors note that they did not have information on how mothers-to-be coped with stressful life events or the types of social support they had available.
And they point out that factors other than stress in pregnancy might have been responsible for the increased risk of disease in certain children.
One researcher not involved in the study said it was well designed and addressed an important topic, but urged caution when interpreting the findings.
Alet H. Wijga, from the National Institute for Public Health and the Environment in Bilthoven, the Netherlands, echoed the warning that stress, itself, may not have been what caused kids' asthma and eczema.
"Life events like money problems, job loss and residential move associated with separation or divorce during pregnancy may well have lasting impact on the socio-economic position of the mother and her child and may, for example, be associated with unfavorable indoor and outdoor exposures throughout the child's life course up to adolescence," Wijga told Reuters Health in an email.
"I do think the study provides evidence for an association between prenatal adverse life events and the risk for allergic disease in childhood," Wijga said. The challenge in the future will be to sort out the possible effects of stress during pregnancy from a child's environment growing up, the researcher added.