The research by scientists at Oxford and Exeter universities points to a natural way for women to boost, if only slightly, their chances of having a boy or a girl, depending on whether they consume more bananas and cereals, or have a more restricted diet.

The study, which appeared in the Royal Society's journal on biological sciences, showed that 59 per cent women who ate nutrients including potassium, calcium and vitamins had greater odds of an XY, or male outcome to pregnancy, compared with only 43 per cent of women who rarely or never ate a hearty breakfast.

'The mother seems to be able to influence the survival of either the sperm or the fertilised egg in its very early stages, probably before it has even implanted in the womb,' said Ms Fiona Mathews of the University of Exeter, one of the authors of the study.

These surprising findings are consistent with a very gradual shift in favour of girls over the last four decades in the sex ratio of newborns, according to the researchers.

'This research may help to explain why in developed countries, where many young women choose low-calorie diets, the proportion of boys is falling,' Ms Mathews said.

The study's findings, she added, could point to a 'natural mechanism' for gender selection.

Females are more likely to be born when food is scarce, since they are more likely to produce some babies to ensure survival of the species.

But if conditions are not favourable, poor- quality male specimens may fail to breed at all.

'If a mother has plentiful resources, then it can make sense to invest in producing a son because he is likely to produce more grandchildren than would a daughter', thus contributing to the survival of the species, explains Ms Mathews.

AGENCE FRANCE-PRESSE