I had my 1st at 21 & had wanted a baby since I got my first doll. I had my 2nd at 28 & 3rd at 30. I can honestly say now that I have more experience that 19 is probably too young if you have a choice. My mom had me at 17. She thinks she was more mature at 17 than most people in their 30's. The truth is, she wasn't . I remember things she said & did when I was a child, & it wasn't until I was older that I realized it had nothing to do with me, she was just a child herself trying to raise a child. She was responsible, she watched me, fed me, kept the house clean.....but she was still very young to raise a child.
You also don't realize what the responsibilities are and how much having time to earn a better living, have a better education, & have your life really on track will make a difference until your child starts getting older.
If you have a choice, wait. If not, you can be a good mother, just be aware of your choices.