When I was pregnant with my first child my naturally blonde hair turned brown. It seemed to get browner with the other 2 children. Many years ago I started highlighting my hair. I haven't done anything to my hair for about 9 months. It is now blonde like it used to be. In fact one of my children said I was going a little over board with the lightening. Part of it is because I have spent more time in the sun but the lightness is not just on top. I also got a compliment on my nice tan today. I haven't used any sunscreen all summer. I have had more people compliment me in general. It's got to be the iodine.
So it seems that when you are pregnant the baby takes the iodine from you. I know I read somewhere that the reason the first child is sometimes the smartest is because they get the most iodine.