I had the Mirena IUD fitted three months after delivery and I'm worried about the effect on my baby. My doctor didn't tell me the hormones secrete into the milk. I'm really nervous having read this online. No apparent change in supply. Please does anyone have any experience with this. Should I be worried. I'm also reading it can cause breast cancer and you should avoid if your family have a history of it (FDA in the U.S.). I was so desperate for birth control this seemed to be my only option bar abstaining. So much so I completely forgot about my little baby and feeding her.