Note, here be SPOILERS for Game of Thrones if you aren't up to date with the series - and whether or not you're caught up with the novels.
Game of Thrones director Michelle MacLaren has spoken out about that revelation in the most recent episode of Game of Thrones, revealing her thoughts both on the episode itself, and on the direction the series will now be heading in relation to the novels:
"I was so blown away to find out what they are doing with the babies. I thought 'Wow.' I was very excited to do that. I had thought they ate the babies – isn't that horrible?...Dan (Weiss) and David (Benioff) are such great writers. It's exciting to see where they are going to go moving beyond the books, which is starting to happen more and more."
Does this mean we're going to see more surprises for Game of Thrones fans who've already read the books? Short answer: absolutely.
The speed at which the series is being produced compared to George R.R. Martin's writing speed, combined with the license the series is willing and able to take with the source material, is likely to increasingly necessitate plot developments that are yet to appear in the novels. Martin's close relationship with the show is a major part of this being a viable option - the sense is that though tonal changes - however major - may not be run by him, he will have been party to major changes such as this.