Unborn Val'Kyr's are a new battle pet that was added in Patch 5.3.0 (21-May-2013):
The pet spawns in 3 locations in Northrend, but only one is spawned at a time
Unborn Val’kyr are remnants of the blight laid upon the women of Valkyrion by the Lich King. While they may not possess the same undead-raising skills as their fully developed mothers, they can certainly be a bane on other pets. Strictly undead in ability, each one is capable of ripping apart your opponent using spells like Curse of Doom and Haunt. Survival, of course, is merely relative to these creatures, as they can use Siphon Life to extend their time on the battlefield or cast Unholy Ascension to give your team the edge. Adorable? Yes. Deadly? Double yes!