Confused?!

Elizabeth
Went to the dr for my first appointment two weeks ago at 8 weeks they said the baby looks great saw the baby and the heart beat. Dr told me that after you see the heart beat the chance of a miscarriage falls to 5% or less... That being said does the chance really fall that much more by 12 weeks!? What makes 12 weeks special I thought it was because the risk went down but by how much more?