The reason why eggs are marketed as Fertilized is just a marketing ploy. They sell for more $$$ to the same people who pay more for brown eggs..... because they think that those eggs are more natural or taste better, etc. when actually, they are the same nutritionally and are raised in the same manner, except for the presence of a rooster for the fertile eggs.
Now you see all the farms touting that their chickens are "cage free" or "free range" and charging big bucks for the eggs. Cage free means exactly that.... no cage. But instead the birds having lots of room to run around, most are all jammed into a large building and never see the light of day. Free Range means that the birds have access to the outdoors.... however that does not mean they are happily grazing on a pasture. More than likely, their outdoor pen is a dirt pen that is just as crowded as inside the building.
While it is marginally better for the hens to be cage free than in cages, it is still no picnic. Of course there are exceptions, and I would look to small local farms for the best treatment of their hens.
The only thing that I would look for on the label is "ORGANIC" because that effects what my family are eating. As for how they are raised, perhaps those that are listed as "pasture raised" actually are!!
There is not an embryo inside a fertile egg unless it has been incubated for a few days, just a few divided cells that are in stasis.
chel