Fewer boys are being born in central Scotland - and it's thought pollution may be playing a part.
A study by the University of Stirling found that the ratio of boys to girls being born is falling.
While evidence suggests that male babies more often die in the womb than females, it is now thought pollution could be one factor behind this.
Ultrasound: The number of baby boys being born in parts of central Scotland are decreasing
Across the world, slightly more boys are born than girls. But statistics show the proportion of boys to girls being born in Scotland, or the sex ratio, has been on a downward trend since 1960 - and in the industrial parts of central Scotland in particular.
Analysing data from 1973 through to 2010, the team found a 'significant upward skewing' of the sex ratio in the Highlands, compared with a downward shift in the Forth Valley and the Borders.
Researchers found 'significantly lower sex ratios for populations where industrial air pollution is highest' in eastern central Scotland.
The researchers add their findings are consistent with small studies in heavily industrialised parts of Canada and elsewhere in the world.
More research is needed, they say, but warn that care should be taken when planning large industrial developments, as they may have an effect on hormone levels of the local population.
The scientists focused on chemicals or pollution that, at certain and sometimes very low doses, can interfere with the endocrine (or hormone system) in human beings.
Dr Ewan McDonald, the lead investigator, said: 'The reproductive health of populations is often difficult to measure, particularly before pregnancy and at the early stages.
'There is strong evidence that during early pregnancy loss, male foetuses are lost more often.
In utero: Evidence suggests that male babies die in the womb more often than females,
'The sex ratio, particularly declines in male births, can therefore be a marker for changes in reproductive health or fertility amongst human populations.
'Our analysis on sex ratio was extensive: over time, regions, neighbourhoods and socio-economic groups across Scotland.'
He said the results indicate that the effect of pollution on hormones may be to blame for the national decline in the proportion of male births.
Professor Andrew Watterson, also involved in the research, said: 'The study raises important questions about our knowledge of what may impact on human reproductive health and how we then shape public health policy.'
The study is published in the International Journal of Occupational and Environmental Health.
Read more: http://www.dailymail.co.uk/health/article-2665994/More-girls-boys-born-Scotland-pollution-blame.html#ixzz35b8z6lhV
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