I am also a big fan of gel nail. I ask some professional people and they said gel nail is ok as the UV light is very mild which won't hurt the bb. Instead, better try to avoid artificial nail 水晶甲, because the chemical liquid that used for 水晶 powder is very smelly. also, try to avoid nail polish.
I think perming hair is also important issue. For me, I will do it after 3 months, and will pick those salon that use chemical liquid which is less strong. For example I went to a hair salon long time ago, and their perming liquid is so strong that it damaged my original hair without me noticing it. Now, I go to a hair salon with less strong chemical. Also, try to visit the hair salon earlier during the day instead of late afternoon, because the hair salon may full of chemical smell after a whole day of business.
I think dye the hair is not so good for pregnant woman.