I've always heard two reasons why you shouldn't hatch pullet eggs...
1.) because you shouldn't breed a pullet to a mature rooster to begin with. Their bodies aren't fully developed enough to sustain the weight of the rooster, and there is a higher risk for injury.
and
2.) because pullet eggs usually aren't at their full size potential, so as someone has already said, the developing chick will be in rather cramped quarters and can have problems trying to hatch.
With that being said. I recently hatched the first 3 eggs that my Serama hen laid. They were fertile, and I wanted to see what would happen. The first chick to hatch was really weak from struggling out of the shell, and ended up dieing. The second chick to hatch, was strong vibrant and very spunky. The third chick... we'll never know cause my incubator shorted out, spiked to 120 and fried the eggs...
