Climate change could have a negative impact on male fetuses
Monday, October 6, 2014, 2:30 PM - A new study out of Japan suggests that male fetuses are more vulnerable to the effects of climate change and that, over time, could alter humanity's male-female ratio.
According to the study, the ratio of males to females born in Japan has been steadily decreasing since the 1970s, and extreme weather variations could be to blame.
Scientists compared Japan's monthly temperature data between 1968 and 2012 with data on infant birth and deaths rates over the same period.
Researchers also accounted for recent extreme weather events that have been observed in Japan -- like an abnormally warm summer in 2010 followed by a frigid winter in 2011.
It was discovered that there was in increase in fetal deaths during the summer of 2010 and nine months later, more female babies were born than males.
During a cold spell in January, 2011, researchers observed another increase in fetal deaths followed by a similar decrease in male births nine months later.
"The recent temperature fluctuations in Japan seem to be linked to a lower male:female sex ratio of newborn infants, partly via increased male fetal deaths," the researchers write.
The team has only identified a connection and cannot say for sure whether or not climate change is the cause of Japan's shifting gender ratio. Some scientists speculate that other environmental factors -- like pollution and pesticides -- could also be influencing birth rates.
While two other studies, one from Finland and one from New Zealand, have concluded that gender ratios are not influenced by climate, the authors of the Japanese study argue that neither Finland nor New Zealand have experienced Japan's extreme weather fluctuations.
It's unclear why male babies may be more vulnerable to climate change than females.
The full paper can be found in the September 14 issue of the journal Fertility and Sterility.
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