As the placenta starts to reach the end of it's 'use by' date it will start to deteriorate, meaning that the baby doesn't always get as much nutrients as it should be getting. Sometimes it can go a bit gritty (which is also the case with some smokers too) or it can start to calcify, and this can be seen on the u/s. He really shouldn't have left her hanging like that and should have taken the time to explain it properly to her to save her all this worry. I don't know what it would mean for her or her baby though sorry.