Sunday, May 25, 2008

Fewer Boys Born In Industrialized Nations

Fewer Boys Born In Industrialized Nations
A review of birth rates from several industrialized nations shows that the number of male births has declined significantly in the past few decades. Researchers say this change may be tied to increases in male reproductive health problems.
Researchers from the World Resources Institute in Washington, DC, looked at data from Denmark, the Netherlands, Canada and the US, and found similar declines in the sex ratio, or the number of male births per female births, in these countries. For example, from 1970-1990 in the US, the reported decline of 1 male birth per 1,000 births resulted in 38,000 fewer male births. And in Canada, the decline of 2.2 male births per 1,000 births resulted in 8,600 fewer boys being born during the same period.
"Such small changes... can have profound implications for large populations, where hundreds of thousands or millions of births occur each year," write Devra Lee Davis and fellow researchers in The Journal of the American Medical Association.
The investigators explain that several factors influence whether a fetus, which starts out female, becomes male. Exposure to hormones, older age of fathers, use of fertility drugs, hepatitis and non-Hodgkin's lymphoma may all reduce the proportion of male fetuses. Workplace and environmental factors such as "...exposure to smelting operations, pesticides, inorganic borates, lead, solvents, (and) alcohol" have also been linked to reduced male populations.
In addition to the concerns about the reduced male birth rates, Davis and colleagues note that disorders of the male reproductive tract, such as hypospadias (an abnormality of the penis where the urethra opens on the underside rather than at the tip) and cryptorchidism (a condition where the testes don't descend normally) are becoming more common. The researchers suggest there is a link, and theorize that prenatal exposures may affect men's overall health and development.
The authors call for additional studies about birth rates by state, region and nation. "The potential repercussions of conditions that may alter the ratio of the sexes at birth should be considered a matter of utmost concern," they write.
SOURCE: The Journal of the American Medical Association

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