According to research reported by the BBC, a female’s diet around the time of conception may influence the gender of her baby. The study, by the Universities of Exeter and Oxford, appears in the Royal Society journal Biological Sciences, suggests a high calorie diet at the time of conception, especially proper breakfasts, might increase the odds of a boy, and that the modern trend to opt for low calorie diets might explain why the proportion of boys is falling in developed countries.
While the data is probably consistent with the conclusion, there are likely to be other factors involved. I’ve conjectured for a long time that the incidence of stress factors is what influences the gender of the foetus: if the mother is under stress then she will tend to produce a female, if she is not then a male. Why? Because females are necessary for the protection of the species. One male can fertilise many females. If the species is under stress it can rebuild with lots of females and few males, but not the contrary. In relation to the study, being well fed would indicate low stress and therefore its OK to have males, which are (sometimes) good for doing the heavy lifting. Research into other factors related to lifestyle and health are likely to support the conjecture that a low stress environment produces males, while a higher stress environment produces females. I would also qualify the hypothesis with the note that a change in stress level is significant; in other words, if getting married is a stressful change in life the mother will produce females first, whereas if it is a happy change she will produce males.
Until any hypothesis becomes more significant, the best indicator of the likely gender of a baby is … chance.
And be thankful that you are not a French man in the 18th century wanting a boy, as this BBC article discusses at the end.