Copper
"Hi, I'm 28 yrs old and got 3 kids already. I've had the IUD for about a year now, and I'd have to say that personally it has worked wonders for me. 
I'd encourage women who have had the IUD inserted to got for an ultrasound at least twice a year. 
I had my second scan last week and the device is still intact where it should be, with no abnormalities found.
Yes I did experience cramping a few days after it was inserted, by after that I did not experience any complications.
Although I don't think it should be recommended for all women, I really depends on how each individual reacts to the method and whether or not she is comfortable with it."