Hatching Pullet Eggs: Just Say “No”
Squee! Your pullet laid her first egg and it is so pretty and cute and you want more. You want to hatch this precious little egg.
There are several reasons one should not hatch the pullet eggs — a pullet being a female chicken prior to her first molt, at which point she becomes a hen.
Lymphoid Leukosis. If your flock has a carrier she can pass it on to the chicks through the egg, but the rate of transmission reduces by about 95% after her first molt.
Her Reproductive system is just starting up. Many humans CAN reproduce at 10 or 11, but if they did, would you expect healthy vibrant off-spring? It’s no different with a chicken.
The egg is so tiny, the chick will not have enough room to grow, pip, and zip properly.
I know it is tough to wait, but for the health of your flock it is for the best. Further reading: Can You Incubate Pullet Eggs?

All my best tips for hatching healthy chicks with loads of pictures and videos.
The information that used to be here has been folded into my article on Incubation & Hatching Tips: LockDown & Hatching. I just left his page up so if google sends you here you don’t hit a dead-end.
Watch from pip to zip. 8 seconds time-lapse.
Squee! Your pullet laid her first egg and it is so pretty and cute and you want more. You want to hatch this precious little egg. But don’t.
One thousand, three hundred, and fifty-six chicks later, and I still get excited when they hatch. Live-stream hatching link in the post.