I believe that the acceptable age to have a child is different for everyone. Levels of maturity differ between people of the same age - some people don't feel ready till they're thirty, some twenty etc. Some people want a career first and some want to be a full time parent above anything else.
I think what I am trying to say is that the acceptable age is your decision - try not to let people tell you your too young if you feel you aren't.
I was pregnant with my first at 24 and my husband and I look MUCH younger than we are (my husband is younger than me!) and people often commented on us being too young but we just ignored it. We have had nothing but support from our families and friends.
My pregnancy was not planned but we couldn't be happier. I always wanted to have children young. My husbands parents were 20 when they had him and they said it was great - they all grew up together. His mum is only 44 now and she says shes glad she did it so young and she is also a young grandmother!
4 lovely munchkins DD 10/03, DD 03/05, DS 10/06 &