You should be careful having an IUD while being poly Kali. They increase the risk of contracting an STD, which is part of the reason I got rid of mine. Sucks too, because they're really convenient.
All types do? If not, which type?
Also, I've never heard this. Source?
Honestly, either way, it's not like there's much of an alternative. I got it initially as emergency contraception (a couple weeks after my old one malfunctioned) because I couldn't take the morning after pill. Well, I did take that, too, but with a ~40% failure rate (liver enzymes, blah) it wasn't really very useful. There's always something up with my liver... or too often to go for a different mode of contraception. I mean, there was a period where it was okay, but I couldn't take it now (not that I need to in Pakistan) and that just happens periodically. A lot
of common medications render the pill useless.
...and what other options are there?