Rush Limbaugh overlooked the mechanics of the morning-after pill to liken it to an abortion drug, ignoring that Plan B does not terminate a pregnancy and must be taken within five days of intercourse to be effective.

On the November 25 edition of The Rush Limbaugh Show, host Limbaugh highlighted a European company's claim that its version of Plan B, the emergency contraceptive pill, may be less effective in women who weigh over 165 pounds. Limbaugh speculated that because of this announcement, a pregnant woman who weighs more than 165 pounds and wants to end her pregnancy must either go on a diet before taking the morning-after pill or get an abortion:

LIMBAUGH: Now we have learned that American women, 166 pounds and up, the Plan B pill doesn't work. What will their option be? 166, 170 pound woman, pregnant, she wants to go ahead and get her morning-after pill, and then she's told, 'Sorry, you're too big. You're too heavy. It won't work.' What are her options? Well, she can either go on a diet, or she can get an abortion.

Limbaugh demonstrates his misunderstanding of the mechanics of female anatomy and emergency contraceptives.

Plan B, the morning-after pill, prevents pregnancy. It works by delaying ovulation and preventing an egg from being released for fertilization, or by immobilizing sperm. It makes sense, then, that the pill must be taken within five days of intercourse to be effective.

It takes a lot more than five days for a woman to know she's pregnant -- tests generally don't produce positive results until after a missed menstrual cycle. And once a woman is pregnant, Plan B is no longer an option to end the pregnancy. The pill has not been shown to stop implantation once fertilization has occurred, as The New York Times explained [emphasis added]:

Studies have not established that emergency contraceptive pills prevent fertilized eggs from implanting in the womb, leading scientists say. Rather, the pills delay ovulation, the release of eggs from ovaries that occurs before eggs are fertilized, and some pills also thicken cervical mucus so sperm have trouble swimming.

Limbaugh went on to theorize that Planned Parenthood is behind Plan B's alleged decline in effectiveness for women over 166 pounds:

LIMBAUGH: So what are the possibilities that Planned Parenthood injected some kind of a germ into these pills to make them not work on women over 166 pounds? I like putting my own conspiracy theories out there just to toy with people. But Planned Parenthood is going to be a clear beneficiary here, of this little factoid about Plan B not working in women over 166 pounds. 

Limbaugh's misunderstanding of the morning-after pill comes as no surprise given his longstanding, willful ignorance on women's health issues.