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BBC News Online: Health

Wednesday, 15 March, 2000, 02:42 GMT

More boys 'born in warmer countries'

The chances of giving birth to a boy increase as you head south, researchers have said.

They studied birth rates across Europe and found the proportion of boys over girls rose with the temperature.

The countries to the south of Europe have a significantly higher number of male births than those towards the north of Europe
Dr Victor Grech

The research team at St Luke's Hospital in Malta could not suggest why this might be the case, but suggested warmth might affect fertility and gender ratios.

Previous studies conducted in Denmark, the Netherlands, Canada and the US have shown a decrease in male births over the past three to five decades. But there was no similar drop in Malta, prompting the investigation into the effect of climate.

World-wide, 51.5% of births are boys. But the research team led by Dr Victor Grech found the ratio varied "significantly" from northern to southern Europe.

In Scandinavia, 51.2% were boys. In Central Europe - stretching from the UK to Poland - it was 51.3% and in Mediterranean countries, including Spain and Italy, it was 51.6%.

Less fragile

It is known that the female foetus is less fragile than the male foetus, which is more prone to the effects of the environment on pregnant women.

Dr Grech said in the Journal of Epidemiology and Community Health: "The countries to the south of Europe have a significantly higher number of male births than those towards the north of Europe.

"It is not possible to identify factors that have led to the differences in these sex ratios at birth. An obvious potential factor is that of temperature."

Professor Ian Craft of the London Gynaecology and Fertility Centre told BBC News Online: "I have no idea why that would be. It is fascinating if it is true.

"One report is of interest, three consistent ones would make it really interesting."

He pointed out that the general temperature would make no difference to the internal temperature where fertilisation takes place.

He added: "That is the fascinating thing about fertility - you have to think about every possibility."

Related to this story:
Morning sickness 'worse for mothers of girls' (10 Dec 99 | Health)
Doctors oppose home births (23 Aug 99 | Health)
Problem births 'no greater in industrial areas' (10 Sep 99 | Health)
Stress makes baby girls more likely (27 Aug 99 | Health)

Internet links: British Fertility Society | Issue - National Fertility Association |
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Health Contents: Medical notes | Background Briefings |