Pro-choice is a decidedly liberal view, being pro-choice means one supports women's individual civil rights to seek information and to decide whether or not she is ready (physically, emotionally, socially and financially) to reproduce, and have legal access to the means to act upon that decision.
Who is pro-choice
Those who are pro-choice generally support a woman's natural right to choose how to use her body, especially in her choice of medicine, reproduction, and sexuality. Those who are pro-choice generally agree that women never ceded their natural reproductive rights to government, and government has no legitimate power over these private individual decisions. Those who are pro-choice are likely to support reproductive education and to be pro-contraception as well. People who are pro-choice are not necessarily pro-abortion. It's like Barack Obama, who is pro-choice, has said "no one is pro-abortion". Being pro-choice simply means believing that a woman should choose what happens to her own body and should not be forced to carry a baby unless she wants to. People who are pro-choice are likely to think the policy in Communist China of forcing women to terminate wanted pregnancies is cruel as do other people.
Being pro-choice can also mean believing the state should provide better child care facilities so women are not forced to choose between career and motherhood or college education and motherhood. Also women shouldn’t be forced into poverty if they choose to continue a pregnancy, see Bad reasons for abortion.
In addition, pro-choice can mean girls can put their child up for adoption, then everyone's happy. There is a low chance she will ever meet her child again, the child will have a good home free of poverty, and the girl can go to school. However; often girls never get over losing their child to adoption. Incidentally abortion rates are regularly lower under Democratic Party administrations because liberal policies make it easier for women and girls to access contraception, also make it easier for women and girls to keep their babies when they become pregnant.
The opposite of being pro-choice is called being "pro-life" a typical disinformation tactic of the Neocon spin machine. There is a certain irony here, as most pro-life conservatives also support capital punishment (not particularly conducive to life) and "wars of choice," which have the nasty habit of resulting in hundreds of thousands of "accidental deaths" called "collateral damage." This implies that a spherical layer of around 128 cells surrounding a central fluid-filled cavity has more right to live than an Iraqi family of four. Pro-life’ers also tend to be against Universal health care and inadequate access to doctors caused unnecessary deaths among uninsured Americans at all ages.
Women and girls who actively campaign against abortion sometimes need abortions themselves. When that happens they often decide that they personally are right to choose a termination but all those other women are sinners, see Joyce Arthur, "The Only Moral Abortion is My Abortion": When the Anti-Choice Choose.