I dont think that there is one pat answer to that question.
I think the human body has its own innate wisdom. A female body wouldn't be "able" to conceive if it were not meant to. So BIOLOGICALY you have one answer.
As for emotionally? Heck no. Not in todays modern world. Something has happened to make that so. We have undergone the feminist movement where we have been persuaded to think that "choices" and "careers" are our fast track to fulfillment.
100 years ago, marriage and children were viewed as the way to fulfillment. Even in countries today that are not struggling to find balance in a post feminist world, the age at which a girl is "ready" emotionally to parent runs younger. The more sophisticated the society - the higher the number is.
I think American girls have been fed a steady diet of how you can "be" anything and "do" anything and the word "choices" sounds very empowering. It is currently very much in vogue to stress this with our young women and girls.
The results are in and they are not good. Remember the pregnancy pact a few weeks back? Also the stats on teenagers getting pregnant is going up. At the same time the stigma of being a pregnant teen is going down, Juno anyone?
What most females seem to want at the end of the day remains the same though - a man that loves them. Children. Financial and emotional security.
I dont think the average American teen aged girl has ANY business having a baby. They have been misled on so many levels about what having a child means, they dont understand that the Spears sisters are not really role models.
The average Catholic girl just a few decades ago, married in her teens and began to produce as many children as she could, as fast as she could. This was viewed as pleasing to God.
While that lifestyle isnt for me - I understand it. The FLDS and mainstream Mormons still strive for the same goal. The fact that I dont personally approve of it for me or my daughter doesn't matter one whit. It is what it is.
As far as the idea that teen pregnancies are more dangerous for the teen - if you go to any reputable web site you will quickly see that it is the American teen life style, that is incompatible with having a healthy pregnancy, that causes those statistics to rise. Things such as drinking, smoking, junk food, lack of prenatal care etc. When (and if) you replace those with a good diet adequate rest and exercise and good prenatal care, the statistical outcomes begin to more closely mirror those of older teens and women.
So just so I am clear...
I think the older the better
I understand that Utopia is just a word
I know that the body has its own timeline and I can work with that knowledge.
I know (as I have said before) that historically Mary, the mother of Jesus was around 14 when she gave birth. She may have been 13 when she got pregnant, we dont know.
I know that even though we have changed a lot socially since then - our bodies are still structurally the same as then.
I know God in his infinite wisdom would have not allowed anything to happen to Mary that was inherently harmful.
I know this post has a high probability of being misquoted.