Double shelled egg

One of our 3 hens has just laid the hugest (!)egg! We were intrigued so cracked it open to find a yolk, white and a fully shelled normal sized egg. We were amazed :-).  Just a bit concerned now that it might have hurt the chicken and may cause her problems. Anyone else had experience of this?

Thanks.

So which came first - the chicken or the egg or the egg?

I expect your girl will recover, but it's very interesting.  Any pics??

Hopefully it's just "one of those things" and will not happen again, but do keep an eye on her in case it's a sign that her egg-laying system is not working as it should.  As long as she is alert, active and doing all her usual chickeny things you should have nothing to worry about.

Apparently this happens when an egg goes all the way through the system, but instead of being laid it goes into reverse and heads back up the reproductive tract.  Then it meets up with the next yolk coming the other way, and the system treats the whole lot like one egg, covering it in white and putting a shell on it.

Eggs really are amazing.