Is it ever ok to announce a pregnancy at someone else's event?

Si & Gary 16/11/2017

We recently received an email from someone who was left feeling a bit upset by one of their friends.

The anonymous emailer was hosting a house warming party with her fiance when one of their friends announced she was pregnant. The couple were left feeling a bit annoyed by the whole thing, in their eyes it was their event and wasn't her place to announce the news.

Gary was dead against it, but will the rest of the team agree?