Pro-life utilitarians are very scarce. A philosophy professor recently told me that he knows of zero pro-life utilitarians in the entire philosophy profession.
This is deeply puzzling. While I'm not a utilitarian, the utilitarian case against abortion seems very strong. Consider: Even if a pregnant woman deeply resents her pregnancy, she is only pregnant for nine months. How could this outweigh the lifetime's worth of utility the unwanted child gets to enjoy if he's carried to term?I expect it hinges on your model of whether abortion simply changes the identity of which children a woman bears or the number of children that would be born.
I don't have any strong priors on which is true on average, but in some cases it would simply be a shifting in timing of births where a woman intends on having a family of fixed size and isn't ready yet to start it. In those cases, and where the woman has reasonable expectations that a child later would be happier than a child now, pro-choice utilitarianism makes a lot of sense.
If instead we're considering options where the number of children isn't fixed and where abortion reduces the number of kids who get to be born, then Bryan's puzzle holds - but doesn't utilitarianism run into trouble where n isn't fixed?