Metal filling removed while pregnant?

Hey everyone, 
Back in January right after I found out I was pregnant I went to the dentist and had a metal filling removed and replaced with a cap. At the time I didn't think anything of it. The dentist knew I was pregnant and did not mention anything about it being unsafe. 
I've just now read that having the metal fillings removed while pregnant is not recommended because it release Mercury during the removal. 
Has anyone else ever had a metal filling removed while pregnant? Were there any issues with the baby? I'm kinda freaked out now about how much Mercury was released when they took out the filling.