I bleached my hair when pg... then I grew too sick of touching the regrowth up, so I dyed it darker. But then the pregnancy hormones must have affected it, as the darker dye would not hold properly, and half of it would come out in the shower, leaving me with washed out orange hair.... I used permanents, and I retouched it every 6 weeks, but it was always the same awful result! Once I had my son my hair was fine again and held onto the dye...
There is divided opinion on the topic of dying/bleaching hair during pg, however the majority consensus that I have heard is that it is perfectly safe...