My son Aidyn was born when I was still 20 years old... I dont see it as being too young at all. I have been around lots of teen mothers in my life, so I would have been considered one of the 'older' ones to have a baby.
There is nothing I would rather be doing now than being a mother. Aidyn has given me more meaning to my life than any sort of career could.

By the time my mother was my age she already had 2 of her children. And by the time she was 28 she had had her fifth (and last) daughter.
She was then able to go onto study at university, and graduate into a full time teaching job, all before the age of 40.

I plan to do something similar to her... I would like to have finished having my babies by my late twenties, and then when they are in school I can concentrate on developing a career for myself.

Personally I think it is incredibly rude of anyone to judge you by what age you decide to have children at. It is not their life, so they should butt out. The people that tell you to concentrate on your career first, are obviously the people that dont have children themselves. As a career (IMO) is incomparable to the overwhelming love and importance that your child will bring into your life.