Boy or Girl?

The environment of the womb can be manipulated to favour either male or female sperm Have a burger and chips before getting pregnant and you're more likely to have a baby boy – whereas a girl is more likely if you eat chocolate or ice cream. It may sound about as convincing as puppy-dogs' tails, but this is the latest cutting-edge science as reported in New Scientist.

Researchers at the University of Pretoria in South Africa found that mice given drugs that reduced their blood-sugar levels produced more female than male pups. And the finding fits with traditional wisdom that mothers should feed on red meat and salty snacks if they want a boy and chocolates and sweets if they want a girl, according to lead researcher, Professor Elisa Cameron.

The team used a steroid called dexamathasone that inhibits the transport of glucose into the blood to study the impact of raised or lowered blood sugar level. "It is very interesting that meat raises blood sugar levels for a sustained period of time while sugar-based snacks are associated with a slump in blood glucose," she explains.

Cameron's study adds to the evidence that a baby's gender is not simply down to whether the father delivers an X or a Y chromosome. The environment of the womb, it is claimed, can be manipulated to favour either male or female sperm.

Over the last half decade, animal research has come up with the same kind of results. Rats fed a low protein diet prior to conception in a Japanese study had more females in the litter, while American researchers reported that a diet rich in animal fat led to more male mice pups.

For Professor Richard Sharpe, head of the Medical Research Council's Human Reproductive Sciences Unit at Edinburgh University, however, the findings are not necessarily good news. "There is a global trend that more girls are being born than boys and the number of girls are increasing," he says. "It's a fractional increase. But all the evidence suggests that the underlying trend is an increase in physiological stress in women that causes the low blood sugar levels that is being reported in the New Scientist.

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