I think it is just an old wives tale. The same as if you have m/s it will be a boy and no m/s it will be a girl etc...

I carried wide with Nicholas (had m/s) and this time I think I am more out the front (no m/s), yet still having another boy.

A woman at the bank yesterday was shocked to find out I was having a boy as she swore I was having a girl by the way I was carrying and how big my belly is!!