As you might know, the sperm of the man determines the sex of the child. The sperm contains 22 chromosomes as well as either an X- or a Y-chromosome. A woman's egg contains 22 chromosomes plus an X-chromosome.

 

If the sperm that fertilises the egg carries an X-chromosome the baby will be XX and will become a girl.

X + X = GIRL

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If the sperm carries a Y-chromosome the baby will be XY, a boy.

X + Y = BOY

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But what factors influence which sperm will be able to fertilise the egg? 

What factors would increase the chances of having a boy, which to have a girl? 

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Many different gender swaying factors have been researched throughout history. 

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The probably most popular and widely spread theory is around timing and was first introduced by Landrum Shettles in the 1960s. He assumed that male (Y) sperm are faster but more fragile than female (X) sperm. He thus promoted the idea that timing would have an impact on gender selection: To have a girl it was recommended to have intercourse a few days before ovulation. However, the theory is controversial with a lack of evidence. Other 'timing methods' (e.g. O+12) and empirical studies question and contradict Shettles findings (e.g. Wilcox et al 1995, Gray et al 1998; click here for more details on timing).

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From all the factors researched on having an impact on gender outcome, the most convincing results have emerged regarding the mother's diet, specifically the intake of certain minerals with evidence gathered over the last 100 years.

 

In the 1920s, a scientist named Curt Herbst made a fascinating observation that would later prove to be groundbreaking in the field of sex determination. Herbst was studying marine worms called Bonellia viridis and noticed that increasing potassium levels in the aquarium water led to a significant rise in male offspring. This discovery sparked further research on the connection between minerals in a mother's diet and the gender of her offspring.

 

Since Herbst's pioneering study, many animal and human studies have confirmed the link between maternal mineral intake and gender outcome and gathered to the body of evidence.

 

Some key ones on humans are:

 

In 1983 the French scientist François Papa published, after many years of research and consulting women who had the wish to conceive a certain gender, a book with the promising title 'Boy or Girl. Choosing Your Child through your diet' (click to read an excerpt). This suggested that a diet high in sodium and potassium favours a boy while a diet high in calcium and magnesium favours a girl, claiming an above 80% success rate.

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A ground-breaking study conducted by reputable Oxford researchers led by Mathews et al. (2008) attracted widespread attention in media and society. The researchers examined the pre-conceptional mineral intake of 740 women in the United Kingdom and discovered a striking correlation between the prevalence of certain minerals and the gender of their offspring. Mothers who consumed higher levels of sodium and potassium in their diet before conception were more likely to give birth to boys. In 2010, Noorlander reported success rates of over 80%. 

 

In 2016 a comprehensive study by scientists around Mahmoud Edessy with a 76% success rate for the desired gender came to the following conclusion: