Only through mind-numbing stupidity could someone suggest that when human sperm and human eggs unite they produce something that is only “potential human life.”
If the word “potential” is suggesting that the unborn is only potentially alive, that is easily disproved.  Even in the earliest stages of pregnancy, sonograms show movements and heartbeats that do not belong to the woman.  Whatever else the fetus is, it is impossible to logically argue that it is not, at least, alive.  

On the other hand, for “potential” to be referring to the word human, a fetus would have to have the potential of becoming either a human being or some other form of life.  Perhaps a parrot or a spider.  Of course, the problem is that there is no record of such a thing having ever occurred.

So while it may be reasonable to say that a fetus is a potential major league baseball star or a potential school teacher, it is idiotic to say that a fetus is a potential human being.  If for no other reason, the fetus is a living human being because that is the only thing it can be.  

Also, if the issue is “development,” let’s not forget that human beings develop for their entire lives.  A fetus is less developed than a newborn just as a child is less developed than an adult.  But being less developed than an adult does not mean that a child is any less a human being.  That’s also true of the unborn.

Pro-lifers aren’t the only ones who know that it is a baby who is killed in an abortion.  At a National Abortion Federation conference in Philadelphia during September of 1994, Texas abortion clinic director, Charlotte Taft, said, “When [a pro-choice activist in the Dallas community] came into our clinic – we were inviting her to learn more about abortions – this is a quote from this woman – she said, ‘If I believed that abortion was the deliberate ending of a potential human life, I could not be pro-choice.’  I said, ‘It would be best for you not to see a sonogram.’”

Less than two years later, at another National Abortion Federation conference in San Francisco, a New York abortion clinic director, Merle Hoffman, stated “...I mean, we are talking about an abortion here.  And uh, also that the staff is uncomfortable when a patient said, ‘I think I’m killing my baby.’  So I’m comfortable with saying, ‘Yes, you are, and how do you feel about that?’”