I exclusively breast fed my daughther for WAY longer than I planned, =). I got the Mirena when she was about 6 months old (and still breast feeding a LOT) and she has only been fully weaned just recently at 19 months. We never had ANY problems, she didn't even notice. And I noticed no change in milk supply. Let me add, that while I feel strongly about things too, I try not to scare people when I recommend against something. I was freaked out by some of these ladies and their cries of "don't do it!" I hope you will consider your own body and previous reaction to hormonal birth control as well as other factors like, do you have heavy menstrual bleeding are you at risk for having it? After my daughter was born it was like someone pulled a cork and my periods were INSANE. I already have an anemia disorder was knew that these heavy periods were hereditary and knew I needed to stem them. I had a HORRIBLE reaction to Yasmin but knew I needed to give this a try before a went the route that can be permanantly sterilizing. I have had no adverse reaction to the miniscule amount of hormones in the Mirena. Also, the hormones in Mirena are localized and not systemic. They are placed where they need to be and do not horn in overmuch on other systems in your body. My periods that were once actually scary for me, are almost nonexistant. Good luck.