Mothers pregnant with male babies eat more than if they had female babies.

Harvard research from 2003 revealed that mothers pregnant with male babies tend to eat more than those carrying females. The research found that women expecting a baby boy consumed 8% more protein, 9% more carbs, 11% more animal fats, and 15% more vegetable fats. Regardless, the expecting mothers of baby boys did not gain noticeably more weight than the expecting mothers of baby girls. 

(source)