Abortion
Which side of the abortion argument you fall comes down to a fundamental point of view on what is the most important moral objective. This can be boiled down to quality of life versus quantity of life and is discussed in detail on that page.
"If men could get pregnant, abortion would be a sacrament." -Florynce Kennedy
Since Quality of Life and happiness are the highest moral objective, the happiness of the living must take priority over that of theoretical future humans. When you factor in the fact that personal freedom is a key component of happiness, there is a strong utilitarian argument in favor of personal choice.
Anti-abortion arguments hinge on a debatable technical definition of human life, combined with the moral trump card of "thou shalt not kill". This is despite the many other exceptions they often make to that rule, such as the death penalty and war. The prohibition against murder in religion is often interpreted as applying only to members of the in-group. It's easier to accept a blameless fetus as a member of your community than it is a murderer or a foreigner.