I'm not sure what it was about the film, but I immediately was put in mind of a modern Grimm's Fairy Tale. Perhaps it was the children's Hansel and Gretel-ness, the acceptance of the otherworldly in apparent blissful suburbia, the needs of the parents, particularly the mother, outweighing the love for their children, despite pretending the opposite is true.
Upon finding an egg in the woods, the daughter of an idyllic Finnish family in a well-to-do neighbourhood surreptitiously brings the egg home, hiding it under her pillow from the rest of her family. It quickly grows in size and then when it hatches, something surprising comes out.
Clearly everything is not as it seems, the relationship between the parents is strained and the mother in addition to controlling the life of a daughter who is reaching an age that she begins thinking and feeling for herself is also having an affair. A secret that she seems happy to tell her already troubled daughter all about, without seemingly realising what her daughter is going through.
There are a heap of metaphors here and the layers are many. As much of what is unsaid is as important as the events taking place on screen. The dread is consistent throughout as the eponymous hatching develops over time, becoming more and more protective of the poor girl that raised her. They also appear to develop some kind of psychic bond.
The body horror is well done and there is probably too much vomiting for my liking, although I see the reason why. It's engaging throughout and the casting and performances are excellent.