Traumatic events, such as the 9/11 terror attacks, could lead to miscarriage in women, a new study has claimed.
Researchers have found that the psychological stress of the September 11, 2001, terror attacks caused many American women with no links to the victims to lose their male babies, The Daily Telegraph reported.
This is because the communal bereavement, like the mass grieving after the death of Princess Diana, can bring on high levels of stress, say the researchers.
The study found the foetal death rate for boys spiked in September 2001 and "significantly fewer boys than expected" were born two months later.
Lead researcher Tim Bruckner of University of California said: "The theory of 'communal bereavement' holds that societies may react adversely to unsettling national events, despite having no direct connection to persons involved in these events.
"Our results appear to demonstrate this, as the shocks of 9/11 may have threatened the lives of male foetuses across the US."
For the study, the researchers compared foetal death rates between 1996 to December 2002 to calculate the rate of male fatalities, using data from 50 US States. In September the numbers peaked, they found.
"Across many species stressful times reportedly reduce the male birth rate. This is commonly thought to reflect some mechanism conserved by natural selection to improve the mother's overall reproductive success," Bruckner said.
The findings have been published in the 'BMC Public Health' journal.