Outside of the US it is not uncommon. I believe US eggs are washed with a detergent which kills salmonella and sterilizes any fertilized eggs. As a side effect,

Outside of the US it is not uncommon. I believe US eggs are washed with a detergent which kills salmonella and sterilizes any fertilized eggs. As a side effect, US eggs are more prone to spoiling at room temperature. Anyway, in Europe or Asia one can buy 30 eggs, incubate them for a few days, and hold them up to a lightbox one by one. Probably at least one of them will be fertilized.