The american pregnancy association says that bleaching or dying hair during pregnancy has little to no affect on pregnancy or bby. There is so little of the ingredients used to dye or bleach hair absorbed into the skin it is of no concern. The main concern is if the product used has ammonia in it as it might lead to fume inhalation which could make you sick. After the 2nd trimester it is considered safe to get your hair done. If you work as a cosmetologist you may need to wear a mask in the first trimester to avoid getting sick from fumes.
I would not bleach your hair at this point only 11 weeks to go. If you can wait do it for the safety of your baby.