After many complaints from the fans of Pokémon GO, Niantic finally removed some overly common egg hatches.
In order to diversify the "egg pool", Pokémon GO's new December 16th update has removed over 90 Pokémon that can hatch from eggs obtained via Pokéstops and Gyms. Pokémon from Charmander to Sableye can no longer be hatched. In addition, all baby Pokémon can also no longer be hatched from these eggs.
Removing these Pokémon from the egg pool should make the relatively recently added Unova Pokémon easier to hatch (or at least have a greater chance of hatching). In fact, the Unova starter Pokémon (Snivy, Tepig, and Oshawott) can now be hatched from 2 km eggs rather than 5 km eggs, as it was before. This makes it even easier and faster to hatch these starters.
Eggs received from walking 25 km and 50 km while Adventure Sync is on (connecting Pokémon GO to your phone's fitness or pedometer tracking app) have also been updated. Most Pokémon hatched from eggs via Adventure Sync that were overlapping with the Pokémon that could be hatched from eggs found from Pokéstops or Gyms have been removed, meaning that walking those extra miles (or kilometers) will have a unique and worthwhile reward.
In addition to the removal, the update included five Pokémon that were added to the 5 km egg pool, including Burmy's Sand Cloak, Plant Cloak, and Trash Cloak forms, Pinsir, and Grimer's Kanto form.
However, eggs received as Gifts from friends are not affected whatsoever by this update. If you liked the egg pool the way it was before the update, you can still hatch Gift Pokémon and have access to the 90 Pokémon that were removed.
The egg pool is much, much smaller now, which should make hatching a specific species of Pokémon a lot easier. For a full list of the Pokémon removed from egg hatching from the December 16th update, see the chart made by The Silph Road. This information about the new egg contents was found through their research out in the field.
You can download Pokémon GO now on your phone's app store.
Source: The Silph Road