9/11 Aftermath: More Male Babies Miscarried
That's the conclusion of researchers at the University of California, Irvine, who have been studying the impact of 9/11 on male babies since 2005.
In a smaller study published that year, they found that women in California miscarried more male babies in the year after 9/11 than they did in other years from 1995 to 2002.
This time, the team tracked all fetal miscarriages in the country, using data from the National Vital Statistics System collected between 1996 and 2002.
Their study, published this week in BMC Public Health, included more than 156,000 fetal deaths. In September 2001, the death rate of male fetuses compared with female increased by 12 percent. That's 120 extra losses in a single month.
And because only 10 to 30 percent of miscarriages are reported, Tim Bruckner, the study's lead author and a professor at UC Irvine, suspects the finding is an underestimate.
"The magnitude is reflected in our data, but that 12 percent likely applies to a much larger number," he said.
An evolutionary adaptation is likely to blame for the increase. Experts speculate that male fetuses are more sensitive to female stress hormones. When a pregnant woman experiences some sort of crisis -- whether personal or not -- her male baby is more vulnerable to be miscarried.
In this case, women across the country were undergoing a process of "communal bereavement" -- empathizing with others, even if they hadn't experienced a direct loss during 9/11.
"It's a situation where witnessing harm, even if you don't actually suffer yourself, can actually induce harm," Bruckner said.
Female fetuses are hardier than males, because women have adapted to produce what Bruckner describes as "the alpha male." In times of prosperity and security, male fetuses are more likely to be brought to term, because there's a greater chance that they'll be healthy and robust. During periods of scarcity, however, male miscarriages are much more common.
"A woman's body faces a decision -- evolutionary, not cognitive -- of whether to carry her male baby to term, or abort the fetus," Bruckner said. "If you're pregnant in a time of low resources, there's less impetus for your body to bear that child."
Indeed, the phenomenon reported by Bruckner & Co. has been observed before -- and threatens to become more common. Reduced male birth rates have been reported during other instances of national stress or suffering, like economic recessions or natural disasters.
And while studies have yet to examine whether the recent recession led to an uptick in male baby miscarriages, Bruckner says it's "a logical extension" of his team's findings.