Exposure to stress in the womb might affect a man's fertility in later life, finds a new study.
The research team from the University of Edinburgh and Medical Research Council looked at the effect of stress hormones - glucocorticoids - combined with a common chemical used in glues, paints and plastics.
And found that the combination strikingly increased the likelihood of reproductive birth defects.
These include cryptorchidism, when the testes fail to drop, and hypospadias, when the urinary tract is wrongly aligned. The conditions are the most common birth defects in male babies.
During the study, the researchers examined the male fetal development in rats.
It found that while exposure to the chemical compound dibutyl phthalate - present in products including glues, paints and plastics - had some effects on reproductive development, this was significantly increased with simultaneous exposure to stress hormones.
"What the study shows is that it is not simply a case of one factor in isolation contributing to abnormalities in male development but a combination of both lifestyle and environmental factors, which together have a greater impact," said Dr Mandy Drake, at the University of Edinburgh's Centre for Cardiovascular Science.
"In most studies reproductive disorders are only seen after abnormally high levels of exposure to chemicals, which most humans are not exposed to.
"Our study suggests that additional exposure to stress, which is a part of everyday life, may increase the risk of these disorders and could mean that lower levels of chemicals are required to cause adverse affects," Drake added.
The study is published in the journal Endocrinology.