Final answer:
Mifepristone (RU-486) must be taken within the first ten weeks (70 days) of pregnancy to induce an abortion, and it is distinct from emergency contraception like the 'morning after' pill.
Step-by-step explanation:
Mifepristone (RU-486), which can be used to induce abortion, must be taken within the first ten weeks (70 days) of becoming pregnant. It is part of the medical abortion regimen that involves taking mifepristone followed by another medication, misoprostol, some time later. It's critical to note that mifepristone is distinct from emergency contraception, such as the "morning after" pill, which can be taken within 72 hours after unprotected sex to prevent pregnancy. Medical abortion with mifepristone and misoprostol is a voluntary termination of an existing pregnancy, which is different from emergency contraception that prevents a pregnancy from occurring.