... not you, that is, but your dwellers.
Normally, when "magic happens" between a male and a female dweller in the living quarters, happiness of the both of them soars (usually going to 100%). However, twice now, I have actually had the woman's happiness drop to 10% as she became pregnant. It recovered eventually, but it's still a curious occurence. I generally try to keep my dwellers happy, so this was a nasty surprise.
Is there a way to predict when this will happen, and prevent it?