What Are The Risks Of Doing Medical Abortion After Nine Weeks?

How come some doctors will do a medical abortion after 9 weeks to 12 but most will do up to 9 weeks. Is there a higher health risk and when Doctors do a medical abortion after nine weeks, I heard that they use a lower dosage of Mifepristone and Misoprostol and I have also heard a lower dosage of Misoprostol.Are either of these true.