Levonorgestrel
"I've had the Mirena since 2004.  I had my first one removed after 3 years and was pregnant within a month!  At my 6 week appointment I had another inserted.  Three years later, we wanted another child and were pregnant in a couple of months.  Amazing.  I will admit, after the first one was inserted I cramped and it was miserable for two weeks.  Every one since went in easy and out easy.  I've had no period to speak of for years. I'm coming up on the five year mark and am totally planning on another!"