Answer:
Chicken eggs can be compared to human menstruation when unfertilized. A chicken egg is already fertilized or unfertilized when the shell forms around it in the hen. A fertilized egg could potentially produce a chick. An unfertilized egg will never produce a chick.
However, fertilized eggs do not begin to grow until they are incubated (in an incubator or under a brooding hen). This allows the hen to lay several eggs over a period of days to incubate, but still have them all hatch at the same time.
A human abortion or miscarriage occurs after the fertilized egg has implanted and started to grow, so to duplicate this with a chicken egg, the egg would need to be taken from under an actively brooding hen, or out of an incubator. A fertilized human egg that fails to implant is not considered a miscarriage, so removing a fertilized egg before the hen has begun to brood on it would not be comparable to an abortion.