I can't say all preg teens are more mature than the others but a vast majority of them are. Now, they may have made a bad decision by having sex unportoceted or otherwise - but does that make them any less of a better person or any less mature? No.
The reason I believe being pregnant makes you more mature is because you are faced with endless responsibilities, and no way to go back and fix it. What's done is done. You have no choice but to grow up and face what it comming. You are going to be the nurturer to someone else. You are going to care for another life above your own. A lot of preg teens realize this, and that is what makes them mature. They are facing parenthood. Which believe me, is no easy feat.
The maturity issue in all of this is being accountable for your actions, taking responsibility.....Other teen girls don't have anywhere near the choices to make, or responsiblity to take care of...so how can they be more mature when they have never faced something of this aptitude? There biggest problems are thier grades, clothes, and which boy is asking them out. A mother has so much more to tend to.
I know, because I got pregnant at 17, got married when I was 18. Now I am almost 21, and I see I missed out on a lot. But to me it was worth it. Yeah, I grew up a lot faster than some other girls, but so what? Look at what I have. I wouldn't trade my 2 kids for the world.
FYI for the one that said something about having one with a 2 yr old. My son will be 2 in dec, my daughter will be 1 in nov. And even though things were hard. I, myself, WOULD do it over again. Don't speak on something you know nothing about.