Hi Bess,
I cant tell you anything about the medical side of things but I can tell you for sure that the whole balance thing is just thrown out the window!! hehe
I wore high heels for years for work and when I was pregnant I wore them up to about 3 months and once I started showing and my belly started to stick out ... well once my centre of gravity changed it was HALERIOUS!!! I could not stop myself from walking forward as such... my whole body just wanted to lean. It looked very funny when I caught my reflection in a window one day!!
So I went home and retired my old girls and have only worn them once since having bub... Now that was a funny story too!!

I was told by many people that if you can wear them comfortably then go for it... but I guess you better seek some medical type advice.... Just in case

xox