How to control sex of your baby: Scientists make groundbreaking discovery that could help determine gender

Old wives tales have long claimed to help predict the sex of unborn babies - but this goes a big step further

Tony Whitfield

19:11, 12 Jan 2017Updated 11:29, 19 Jan 2017

Those trying for a baby who have higher blood pressure are more likely to give birth to a boy, the groundbreaking research suggests(Image: Getty)

Women can control whether they have a boy or a girl by raising or lowering their blood pressure before conceiving, a new study found.

Those trying for a baby who have higher blood pressure are more likely to give birth to a boy, the groundbreaking research suggests.

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Old wives' tales about predicting the sex of unborn babies - including dangling the mother's wedding ring on a thread to see if it swings or moves side to side - abound, but now scientists believe blood pressure could hold the key.

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A team at Mount Sinai Hospital in Toronto, Canada, found that women with the highest blood pressure readings were around 45 per cent more likely to have a boy than those with the lowest(Image: Getty)

A team at Mount Sinai Hospital in Toronto, Canada, found that women with the highest blood pressure readings were around 45 per cent more likely to have a boy than those with the lowest.

Dr Ravi Retnakaran, the lead researcher, said their findings “suggest that a woman’s blood pressure before pregnancy is a previously unrecognised factor that is associated with her likelihood of delivering a boy or girl”.

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Lifestyle choices, such as smoking, drinking too much, not exercising and getting overweight, lack of sleep and stress all lead to abnormally high blood pressure, known as hypertension.

Parents often specifically want a boy or a girl but have always believed that it was out of their hands

To examine whether blood pressure had a role in determining sex ratio of babies, Dr Retnakaran recruited 1,411 Chinese women who were planning to have a child in the near future to an unique pre-conception cohort.

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The women had a medical at the start and during pregnancy and had their blood pressure, cholesterol, triglycerides, and glucose measured.

They were assessed at median 26.3 weeks before pregnancy and resulted in the births of 739 boys and 672 girls.

After adjustment for age, education, smoking, BMI, waist, cholesterol, triglycerides and glucose, mean adjusted systolic blood pressure before pregnancy was found to be higher in women who subsequently had a boy than in those who delivered a girl - 106.0 versus 103.3 mm Hg.

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You could be able to design your own family(Image: Rex)

But Dr Retnakaran warned the findings "could be particularly problematic and potentially dangerous in populations which may favour the birth of one sex over the other" as a mother's blood pressure could be artificially manipulated.

He said the sex of a foetus was determined by the sex chromosome of the fertilising sperm, with spermatozoa carrying a higher proportion of Y chromosome yielding boys, while more X chromosome producing girls.

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But the results of his team's study shine a light on another potentially very important factor in determining the sex of babies and how it could be engineered.

The study was published in the American Journal of Hypertension.