A.,
I have to agree with Tonya. Any form of hormonal birth control (rod, ring, pill, Mirena IUD) or the Copper IUD (Paragard) works in multiple ways--suppressing ovulation, acting as a spermicide, etc.... but all work (at least secondarily) as an abortificant by preventing the implantation of a fertilized egg. I really, really do not want this to be true, as I would love to get and IUD after by second baby is born in April. However, after much research, I cannot in good conscience use a method that would prevent a fertilized egg from implanting. I realize that everyone has different views and opinions on this matter, and I am not trying to force my view on you or make you feel guilty, but if you are concerned about this (which your question seems to indicate) than the only options are barrier methods such as a diaphragm, condoms, cervical cap, sponge, spermicide, etc... or the Fertility Awareness method (also called sympto-thermo method) which can be difficult to practice during breastfeeding due to night waking and lack of periods. My plan after pregnancy is to use a diaphragm with a spermicide until my periods are regular again or we make a decision on whether we are done having babies or not (I am not quite ready to decide that right now!). Anyway, good luck on this decision. If you choose to do the research, you can look up any brand name's package insert online (usually there is a link from the website) and check under clinical pharmacology or Mechanism of Action. It gets a little technical, but they all talk about alteration of the uterine lining to make implantation less likely. I would be happy to send links to specific options you are considering if you want to PM me. Again, I did all the research HOPING for a better option that I could stomach morally, but I didn't find one. Good Luck.