Yes it's a build up of fluid in the womb so maybe it was just a term used in Suffolk for the womb dropping down. Things were often getting "dropsied" in my house!
It's sad that your mum couldn't share Annie but, even now, it's difficult for us to talk about such a personal thing as prolapse so it would be something that she kept private and to herself I would think. I still feel it must have been something I did - although the pelvic floor nurse is working hard to change that view!
Taz x