An interesting medical issue

"The Walking Dead" characters mistakenly think the morning after pill causes abortion. Do the writers?

I wasn't aware that there was a debate about how the "morning after" pill works, but apparently there is:

Morning-after pills are not abortion. You can't even get abortion pills from a typical pharmacy, since RU-486, the actual abortion pill, is dispensed mainly at doctor's offices. Morning-after pills are contraception, and they work by stifling ovulation before any sperm can make their way toward the Fallopian tubes. Anti-choicers claim they work by preventing fertilized eggs from implanting, but there is no scientific evidence for this claim, and strong evidence against it. But even if you mistakenly believe this is how emergency contraception works, that still has no bearing on pregnancies that have already begun and show up on pregnancy tests, as portrayed on this show. She might as well have been sucking down candy cigarettes in hopes of causing an abortion.

That link leads to this abstract:

A major barrier to the widespread acceptability and use of emergency contraception (EC) are concerns regarding the mechanisms of action of EC methods. Today, levonorgestrel (LNG) in a single dose of 1.5 mg taken within 120 h of an unprotected intercourse is the most widely used EC method worldwide. It has been demonstrated that LNG-EC acts through an effect on follicular development to delay or inhibit ovulation but has no effect once luteinizing hormone has started to increase. Thereafter, LNG-EC cannot prevent ovulation and it does not prevent fertilization or affect the human fallopian tube. LNG-EC has no effect on endometrial development or function. In an in vitro model, it was demonstrated that LNG did not interfere with blastocyst function or implantation.

Interesting...