The sex of new babies is influenced by the mother’s diet before she conceives, a new study suggests. According to a survey of 740 British mums to be, a high-calorie diet is more likely to lead to a baby boy in nine months’ time. Researchers led by Fiona Mathews of the University of Exeter collected data on the pre-conception dietary habits of pregnant women, and found that 56% of women in the highest one-third of calorie intake had male fetuses. In the lowest third, only 45% bore boys.
The women, who were attending maternity clinics, were asked to compile a ‘retrospective diary’ of their food intake in the weeks before they fell pregnant. Mathews and her colleagues then analysed the results to look for a relationship between food intake and the sex of their offspring. The level of calorie intake was the main dietary factor that affected offspring sex, say the researchers, who report their research in Proceedings of the Royal Society B. Overall, women in Matthews’s study who produced sons ate an average of 180 calories more per day than those who had daughters — “the equivalent of eating a banana”, she says.