bleaching hair pregnant

I'm 34 weeks and I haven't died my hair in just over a year so my roots are maaaaad! I've booked in the hairdressers to have my roots bleached as I have blonde ends and light brown roots, is it safe to bleach my scalp with a lower peroxide rather than high lights?? I think I'll need it roots fully bleaching as it's so long my roots rather than in foils, any one know if it will be okay???