Miscarriages of male fetuses increased significantly in the US after 9/11 likely due to stress, scientists believe. Researchers discovered that 12% more male fetuses were lost in the 20th week of pregnancy than in a "normal" September. Fewer boys were born in all states up to 4 months after 9/11. Scientists blame "communal bereavement," which is acute mental distress linked to a major national tragedy, even if the pregnant woman has no direct connection to people involved in the event, notes the BBC.
Pregnant women and male fetuses are particularly sensitive to such stress, scientists believe. "Across many species, stressful times reportedly reduce the male birth rate," said lead researcher Tim Bruckner, who believes the miscarriage rate was actually significantly higher because they tend to be under-reported. "This is commonly thought to reflect some mechanism conserved by natural selection to improve the mother's overall reproductive success." (More 9/11 attacks stories.)
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