My brother in law often said ( in front of his kids) " I think my kids are smart enough to not get pregnant as teenagers." Sometimes a Dad or an Uncle can make a statement that makes a definite impact. His kids were in their 20's and married when they had their 1st babies.
Oddly, enough our son as a child and as an early teen wanted a baby. He'd say "I'd be a better parent than a lot of other people."
I'd say, keep in mind a baby doesn't belong to one person. Legally, you may be forced to send the baby to the other parents house (even if that family is somewhat unfit.)
You'll probably have to share custody, probably pay some child support. A parent has to work while in high school, then attend college or trade school. That doesn't leave a teen parent much time to play with the baby.
It doesn't sound like you, or other teens are planning to get married. More than likely, you wouldn't be sleeping in the same house as the babies mother. How well will you sleep at night when your baby is at the birth mothers house? Can you trust she'll be home or will she be out partying? Will she wake up in the night to feed the baby or make sure he's in dry diapers and warm pajamas?
The conversations must have worked. He had his 1st child at age 24 three years ago. Our daughter age 29 her first child, just last month.
Playing devils advocate by pointing out the legal & financial effects were effective. A little verbal jousting on parental legal rights responsibilities will be good for her and keep you on your toes.
These were conversations were not done as serious one on one talks. Specifically, when I'd hear a baby related detail on the TV news or learn of a teen pregnancy, I'd be peeling potatoes in the kitchen, then I'd spout off about what could possibly happen to this baby and its parents rights in the future.
My kids were not squirreled away in their bedrooms. Our only TV, phone and computer were in the family room next to the kitchen.
Amazingly, our house was "kid central." My kids and their friends were constantly close by to hear my comments. I always let them tell me what they thought (in a respectful manner.) (Calling me dumb or clueless doesn't cut it in my house!) My kids and their friends learned to debate and question in a calm respectful manner. If not I'd say "try saying that again pretend you are talking to a judge in a courtroom custody case."
As adults these kids are analytical and expressive in their manner of speaking.
Best Wishes