The theory, outlined in a report by the London School of Economics, may help couples predict whether they are fated to have only girls — or boys.

The study may also reinforce some stereotypes of the sexual division of jobs. The researchers came up with their conclusions after studying the careers and families of 3,000 people from various professions.

The report, published in the Journal of Theoretical Biology, links maleness to “systemising” jobs such as engineering which require precise and detached judgment. Femininity, by contrast, is more linked in the study to work that requires “empathising” and human understanding.

Satoshi Kanazawa, the LSE academic who led the research, explained last week that in the general population, roughly 105 boys are produced for every 100 girls.

But according to his calculations, among engineers and other “systemisers”, the ratio is 140 boys for every 100 girls, and nurses have 135 daughters for every 100 sons.

Kanazawa said that a physicist and a mathematician would be the most likely pairing to produce a boy, while it would be worth betting that a therapist and a chat-show host would have a girl.

The study lists insurance executives, architects and management consultants as being among systemising occupations, while empathising jobs include dieticians, careers advisers and those who work with children.

Kanazawa, along with other experts, is unsure exactly why the effect should occur.

John Manning, a specialist in evolutionary psychology at the University of Central Lancashire, said the findings could be due to the effect of testosterone in the womb. Manning said: “High testosterone levels before conception cause a slight excess of sons, but we don’t know why.”

There was evidence that children of systemiser parents encountered more testosterone in the womb than the children of empathiser parents, and were thus more likely to be male.

A study published in 2002 by the University of Auckland, found that assertive women had a higher chance of having a son because of their testosterone levels — indicated by long ring fingers. Meanwhile, Copenhagen researchers have found that smokers are more likely to have girls than boys.

Simon Rogers, 47, an accountant and director of several business consultancies, falls into the systemiser category. He and his wife, Gerry, 40, who teaches maths and computing, live in Penn, Buckinghamshire, and have four sons, aged 14, 12, 9, and 4.

Rogers said that his wife, too, seemed to be a systemiser. “She manages to hold down a job and keep us all fed, clothed and organised in a seamless way.”

The Rogers household is run along highly structured lines, with the movements of all boys and shopping decisions plotted on a whiteboard, over which his wife has ultimate control. Even the youngest son, Toby, is developing into a systemiser. Rogers said: “He will go to the fridge and say, ‘Mum, there are no yoghurts left, can you put that on the whiteboard please’.”

More of an empathising couple are Gerry Baxter, 46, a vet, and his wife, Aileen, 45, a nurse. They live in Dumfriesshire and have four daughters, aged 18, 15, 13, and 11. Baxter said the research “sounds a bit bonkers” but confirmed that his daughters, broadly speaking, showed signs of being empathisers rather than systemisers.

“We have a neighbour with a young child, and they spend a lot of time with him when he comes to visit . . . and as far as tidying their room or carrying out what they are supposed to do, they won’t do it.”

Among the famous who appear to fit the thesis as empathisers are Bob Geldof, the Live Aid organiser, who has three girls and no sons, and Bruce Willis, the actor, who also has three daughters.

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