Parental consent doesn't add much to the amount of abortions. There will also be those parents out there who make their child keep a baby that she does not want or make her have it and give it up for adoption. I think they would balance out the amount of parents who want their child to have an abortion.
Having parental consent for abortion would most likely thwart people from getting abortion rather than encourage it. Teenagers usually want to get an abortion to avoid having to tell their parents they got pregnant, and to hopefully not get in trouble. If they need the consent though then the parents can tell them not to get it.
Parental consent discourages abortion. I had a pregnancy scare in high school. I was not afraid of having a child. I was not afraid of my classmates knowing I was pregnant. I was afraid of my mom finding out that I had sex. I wanted to have an abortion simply so that I did not have to tell my mom and risk her thinking I was a horrible person. I cared more about what she thought than any of the other consequences. I would have had an abortion if I could do it without her knowing just so I could protect myself from her.