Studies Confirm Emergency Contraception Does Not Cause Abortion

NPR:  Morning-After Pills Don't Cause Abortion, Studies Say, by Julie Rovner:

The most heated part of the fight between the Obama administration and religious groups over new rules that require most health plans to cover contraception actually has nothing to do with birth control. It has to do with abortion.

Specifically, do emergency contraceptives interfere with a fertilized egg and cause what some consider to be abortion? . . .