If you picture a U shaped curve, the girl moms seem to be on the extremes of the curve and the boy moms are more often in the middle (with many exceptions.)

My mom has two friends who are both on the heavy side, one has all boys and one has all girls. They have super different personalities, eat different diets, the one with all boys has severe allergies, and also their weight is distributed differently. It's NEVER just about the weight.