I did a small search on line at one point and the only thing I found in relation was that there is a school of thought out there that the shape of the egg indicated the gender and to only set the round ones (as opposed to the oval ones) for girls (I may have that backwards, now that I'm thinking about it too hard). But I found that the hens who's eggs I wanted to set were all pretty consistent in the shapes that the individual birds layed, so I didn't have a choice of shape, Of course, they were nearly all boys that hatched, so I guess it could be that that consistency in shape was because they were all MALE!