And that abortion is illegal. :-)
http://www.biology-online.org/dictionary/Life http://dictionary.reference.com/browse/life
Whether a given bunch of cells may be considered human is still very much an open question but whether a cell or cluster of cells is alive should be pretty easy to agree on.
Actually, a strict utilitarian model would probably conclude that it's not worth aborting to save the mother's life if the baby is viable, since the baby would ultimately produce more value for society than the mother would were she to live out her life.
And that's the sort of reasoning that makes everyone hate utilitarian ethics.
Second, Utilitarianism roughly translates to "the greatest good for the greatest number." If a pregnant, utilitarian woman was granted with the power of foresight, she would abort her child only if he/her was to provide a negative net utility to society. If the child was to provide a net benefit to humankind, she would not abort.
Third, your assumption that unborn (and born) children are a burden to society is correct, but that initial investment is small with regards to the average net "benefit" a grown human creates. It must also be noted that the vast majority of humans benefit humankind through their work (although some have greater impact than others).
No person can see the future, however, so most utilitarians would never abort their children, as the probability their offspring benefit humanity as a whole is greater than the chance that they destroy value.
Frankly, I doubt any woman considers the ethical implications of abortion when they undergo one, and are primarily concerned with family, relationship, and personal problems. If one thinks beyond personal convenience, and look at the bigger picture, abortions are morally unjust from almost every popular ethical system.
Think hard about the choice your parents made by not aborting you. Do you think they made the right decision? Whether you're old, young, rich, poor, hopeful or hopeless, I imagine you'll answer yes.
1. https://en.wikipedia.org/wiki/Legalized_abortion_and_crime_e...