I just found this quote from a Serama breeder.
"I have found Seramas to be very poor breeders. Do not try to breed from very small birds -- especially hens. They just do not have the body capacity to produce an egg that would be capable of hatching. Use medium-sized hens with a small or medium-sized rooster. Show birds are not breeders. Using medium-sized birds will still produce a number of very small show types." -- Jim Archer