The researchers looked at the diets of 740 first-time moms who didn’t know the sex of their foetus. Nutritional data was collected 3 times during their pregnancies: at preconception, at around 16 weeks and later in the pregnancy at 16-28 weeks’ gestation.
Women who consumed more calories around conception were more likely to give birth to a boy. Those that ate ~2,200 calories a day were 1.5 times more likely to have a boy than those that ate less than 1,850 calories a day. No association between the mother's weight and the baby’s gender was found and, in fact, the moms had similar weights. This could mean, although it was not reported, that the women with the higher caloric intake and therefore more likely to give birth to a boy, were more likely to be more active.
Eating breakfast cereals before and around the time of conception was also strongly associated with women giving birth to a baby boy. Women eating more breakfast cereals were 1.89 times more likely to have a boy than those who didn’t consume a lot of cereal and those that skipped breakfast.
Moreover, diets higher in a number of nutrients, including potassium, calcium and vitamins C, E and B12, were also linked to male births.
There was no association between smoking and caffeine intake with the baby’s gender.
Other studies have found that non-nutritional factors have been associated with gender allocation including temperature of the environment, hormonal variations in women at the time of conception and timing of insemination relative to ovulation. These factors may have confounded the results of this study.
This study showed a link between food intake and gender at preconception but intake during pregnancy was not associated with baby’s gender.
Alice Domar, an assistant professor of obstetrics, gynecology, and reproductive biology at Harvard Medical School is worried that women will start skipping breakfast and eating less in the hopes of giving birth to a girl in light of this study. She cautions that its virtually impossible for a woman to change the sex of her baby and a woman's diet has a profound impact on the health of her baby- and that includes folate-fortified breakfast cereals!
Mathews, F., Johnson, PJ., Neil, A. You are what your mother eats: evidence for maternal preconception diet influencing foetal sex in humans. Proceedings of the Royal Society: Biological Sciences. April 22 2008.