The thing you're fine with is a made up science fiction plot device and the thing that would be very problematic in a "real world" sense is something that actually happens in the real world to real people and has those consequences. Except for the "if one is pregnant and then regenerates" bit because that involves the made up thing again and since regeneration tends to happen to the dying and involves all the cells of the body changing (right?) I'd doubt a baby would survive a dying Time Lady regenerating anyway.

I'm left wondering from this episode if there will be a connection to a certain other regenerating woman who 'died/was saved' in a certain library a few years ago.