In Europe, significantly more boys are born in southern countries than in northern latitudes, whereas the reverse is found in North America. The reasons for this difference remain a mystery, according to a study in this week’s BMJ.
Using data from the World Health Organization (WHO), researchers in Malta analyzed and compared the male to female ratio in Europe and North America over 50 years.
Europe was banded by latitude into Southern countries, Central Europe and Nordic countries. The North American continent was divided by latitude into Canada, the United States and Mexico.
The researchers found that significantly more boys were born in southern countries such as Greece, Italy and Spain, than in central Europe or the Nordic countries.
In contrast, a low male to female ratio was found in Mexico, a higher ratio in the United States, and an even higher ratio in Canada.
The authors are unable to explain these findings, but stress that a temperature-related effect cannot account for the differences.
The researchers were from the Pediatric Department, St. Luke's Hospital, Malta, and included consultant Victor Grech.
(Reference: Unexplained differences in sex ratios at birth in Europe and North America, BMJ Volume 324, pp 1010-11.)
(Editor's Note: Full text is available at this URL.)
[Contact: British Medical Association]
26-Apr-2002
