Worm thing in the egg?

So for some reason my muscovy ducklings aren't getting out of their eggs on their own. That hen I talked about a few weeks back I think like people had said she was crushing the eggs trying to help. I have helped 3 in the last day here just get that final little push out. Well today one of them had a smally white worm inside of it when i got it to pop out of the egg? Any idea why or what? Other than maybe a maggot? It was really really really small though. Also why are they having such a hard time getting out of the eggs?