During times of widespread stress, a mother's body may be more likely to spontaneously terminate weak especially male fetuses, a recent study suggests.
The finding adds new perspective to a long-standing debate in population science: Why do male birthrates decline during periods of major societal stress?
The phenomenon has been observed in many animal populations—including humans.
Previous studies have linked the decline in male births to political unrest, natural disasters, environmental changes, and economic recessions.
But scientists are undecided about how and why the decline occurs.
Ralph Catalano and Tim Bruckner of the University of California, Berkeley, School of Public Health reported their findings in last week's issue of the journal Proceedings of the National Academy of Sciences.
Their data support the idea that stressed mothers' bodies may develop a mechanism to reject especially weak male offspring whom they might have otherwise carried to term.
The authors caution, however, that the research has little to do with individual births.
"This is not going to affect anything that you do in the clinic," Catalano said. "There's no impact on how to affect the gender of child. This is about an old and often bitter controversy in population biology."
Females the Stronger Sex?
In general, male fetuses are slightly weaker than females and a bit less likely to survive to birth.
What's more, changes in a woman's body chemistry when she is subject to stress can affect males in the womb more than females. (Watch new 4-D ultrasound video of a baby in the womb.)
|
SOURCES AND RELATED WEB SITES
|
