My hair was straight before pregnant and all the time during pregnancy I did not dare to do anything with my hair.
People always tell me that don't let any chemicals entering your body while pregnant, it will cause problem with the fetus.
The people in hairdressers say that it's OK to do your hair if you are using natural substance.
But you know, there are so many kinds of lotions, used for doing hair, and every shop says that their products are the best, come from natural substance and so on.
So in my opinion the best thing is to avoid doing hair using chemical substance.
It's completely fine if you just cut your hair, or more fashionable, a little highlighting.
The type of doing hair that requires the heaviest use of chemical is perming, this requires strong a lot of chemicals and the ordor is unbearable, that of chemicals for hair dye also stinks, though colouring pose less threat to your baby than perming.
When I was pregnant at later stages, I had to go to hairdresser to wash my hair and just smelling the substance used for perm made me very sick.
Smelling bad thing also affect your mood and hence, the baby (like smoking) so I would not let anybody do anything to my hair.
After all, you are already beautiful when pregnant so why need to do complex hairstyling that requires excessive use of chemicals and hair tools? In case you need to go to party, it's fine to do some styling to make you feel comfortable.
The key thing is that you should always feel and do things that make you happy and beautiful, and pregnancy already brings that gift to you!