Assuming that you accept the principles:<p>a)babies are people<p>b)it is bad for people who are unable to care for themselves to be without care<p>c)teenagers would often be unable to care for their babies<p>one reaches the conclusion that, if teenagers were to have babies, often they would be unable to care for them, and this would be bad.<p>Therefore, reducing the rate of teenagers having babies is good (because it is preventing a bad thing, and not at the cost of another bad thing)<p>Generally, teenagers are not mature enough to raise children by themselves, or, they are at least less well suited than someone a bit older would be.