I dont know whats with people trying to scare a mom to be, specially 1st timers, your body knows what to do, and you will do splendidly, many women smaller than you have been there, done it and they are great, try to relax and ignore bad comments about birth, good luck, congratulations and happy pregnancy!
I have a friend thats 4'11 an she was really small an her an her baby girl is healthy youll be fine people are mean or jelous lol