Before I had my son, I had straight hair, during my pregnancy my hair was a mess. I just couldn't do anything with it. I'm not sure what was going on with it. After I had my son, my hair was wavy/curly. I thought it would change after breastfeeding, but it didn't. My son is 2 now, and I still have my postpartum curls and probably will for the rest of my life. I get a lot of compliments on my curls, but I found the change hard to deal with. I have to relearn how to take care of my hair all over. So, it might go back, and it might not.
I know that BC can effect hair texture too. My friend's hair gets really curly when she is on BC. I had another friend who has fine straight hair, but while she was pregnant she had gorgeous ringlets.