My 2c (against my better judgement)--
I clicked the "It depends" option. Because really, few people favor abortion per se. Rather, they see it as sometimes the best of several difficult options, or believe that it is barbaric to force a woman to bear a child she truly does not want.
On the matter of birth control, there is a lot of ignorance among adolescents and young teenagers. Some think that "If I do it just once," she won't get pregnant.
Also, birth control methods are not failsafe. The failure rate for mechanical barriers like condoms, diaphragms, and cervical caps is unacceptably high. (Between 3% to 12%.) Women are not advised to take birth control pills for their entire reproductive lives, and can never forget to take them. IUDs are safer than they used to be but can cause infections. Permanent surgical interventions are the safest, but typically irreversable. Not a great choice for young people.
The idea that abortion leads to the break-down of the nuclear family is ridiculous. Prior to Roe v. Wade women did get abortions, nicknamed "back room" abortions. Or women tried to induce their own abortions--in ways that were health- and life-threatening. What Roe v. Wade did was make it possible for women who were intent on having an abortion to get one that was medically safe.
Some abortions really are necessary to protect the health of the mother, like ectopic pregnancies that have no chance of fetal survival anyway.
If there is a "break down of the nuclear family" it is more due to society's acceptance of children born outside of marriage. Which is a good thing, from the child's perspective.
Historically and geographically, the nuclear family (mom, pop, kids) is/was not the norm. This was a pleasant 20th century western fiction. The extended family was the norm and still is in many parts of the world.