看医院给发的那本书，copper IUD is effective for 12 years. No side effect and can be used during breast feeding.  Usually, 3-4 week after birth, can be inserted.
The other IUD is effective for 5 year, it released hormone and cannot be used during breast feeding.

I'm thinking to go with copper IUD.


http://en.wikipedia.org/wiki/IUD_with_copper