What happens is that Iodine will send bromine out of the body, and it's the bromine that causes acne. (My mom remembers hearing the same thing when she was a girl.)
Until 1980, a slice of bread would provide the RDA of Iodine (150 mcg). After that, commercial bakeries stopped using Iodine as a dough conditioner and started using its close relative bromine. So all of a sudden instead of getting iodine (good) we began to get bromine, which hardens in fat cells and is very difficult for the body to remove.
When I started iodine therapy a few months ago I had a little belly which I thought was just part and parcel of having had the twins and which would never go away. My stomach is pretty flat now, and I have neither eaten any less nor exercised any more than I normally do. I think the iodine pushed the bromine out. To that end, I did get some "detox breakouts."
Iodine is actually great for the skin. Applied topically, of course, it's a wonderful disinfectant and repairer. One of the doctors who uses iodine said that he has seen it "rebuild the skin from the inside out." I've had the disappearance of what I think was a precancerous frecklish-molish thing. People apply iodine for skin tags and moles to make them go away. 20% of iodine is stored in the skin, and of course it prevents uptake of radioactive materials (it's what you would take in the event of the bomb dropping!) and my theory is that it can prevent or lessen sunburn.
Anyway, as you can tell I could go on, but at least know that it's great that you'll take it during your pregnancy, and that it's pretty impossible to get too much.