IUDs: Understanding How They Work & Misconceptions

Question
Hello and thank you for taking my question:

    I was watching PBS News last night and they were talking about the I.U.D. The republicans said it was abortifactive while the democrats said it prevented fertilization. Could you tell me the TRUTH about this. And also if some are and some arent could you tell me the brand names Id like to read about it. Thank You.

         Pete

Answer
I would say that the democrats are mostly right.  The main way IUD's work is by preventing sperm from getting to the egg.  It's possible that if fertilization occurs, the IUD makes the uterine lining not hospitable for implantation, so one might call that abortifactive.

There is more info here http://brown.edu/Student_Services/Health_Services/Health_Education/sexual_health