"What Research Shows
Data from recent studies continues to provide strong evidence that Plan B does not prevent implantation (this also seems to be true for Ella, another emergency contraceptive option). The majority of research claims that the primary way that Plan B works is by preventing or delaying ovulation--if Plan B is taken before ovulation occurs. By not allowing the egg to release, there is nothing available for sperm to fertilize, thus preventing a pregnancy from occurring."
"In several research studies, women were given Plan B after determining (via hormone tests) which women had ovulated and which had not. The results all showed that none of the women who took Plan B before ovulation became pregnant (these results really help to emphasize how Plan B works by delaying ovulation). Pregnancies only occurred in women who took Plan B on or after the day of ovulation, and these women became pregnant at the same rate as women who have not taken Plan B. Such results prompted researchers Noé, Croxatto, Salvatierra, and Reyes (2011) to conclude that Plan B
“Does not prevent embryo implantation and therefore cannot be labeled as abortifacient.”
How Plan B Works
Sigh
I will also add this.
"In 2007, studies demonstrated evidence that Plan B did not prevent the attachment of human embryos to the uterine wall. Researchers obtained discarded fertilized eggs from fertility clinics. After exposing these eggs to the progestin (found in Plan B) in a simulated environment, results demonstrated that the presence of the progestin did not prevent the eggs from attaching to cells that line the uterus."
"So, the majority of research reveals that using Plan B does not cause any changes in the lining of the uterus (endometrium). Because Plan B does not have any effect on endometrium, researchers have concluded that this emergency contraceptive cannot prevent implantation of a fertilized egg. Many researchers have further explained the notion that Plan B does not stop implantation from occurring is probably the reason that it's not 100% effective at preventing an unintended pregnancy--as well as why Plan B is less effective the longer you wait to use it."
Two different studies have proven it ineffective in causing eggs to not implant... Sigh
This about the third time I have posted this.