Although it would be wonderful if all teens remained celibate, or if they did have sex, used the proper precautions - that's not what happens. It would also be wonderful if all teens felt safe discussing their pregnancy with their parents, but all too often they are way too afraid of their parents to have the conversation - so that's not what happens. Our dreams of what we want to happen are quite different than the reality.
So, if you legislate against teen freedom to choose and to seek medical help without parental involvement, you are actually voting for backstreet abortions, coat hangers, disease, infection and possibly death.
You should not legislate morality. Persuasion, education, kindness are the way to change the world - not new laws.