That's your definition. Is it truly any more right than someone who feels otherwise?
Remember, the issue here seems to be that you couldn't understand why people felt they had the right to regulate what a woman does to her body. If people think she's no longer doing stuff to just her body, but also the body (and life) of the unborn child, wouldn't that make sense for why some people are actually against unnecessary abortions?
And no one is saying that the rights of the fetus are superceding the rights of the woman. In fact, if it is believed that the pregnancy is going to cause ill health to the woman for whatever reason, abortion is the way to go (i.e. the woman's rights are "superceding" the rights of the fetus). And even anti-abortionists are willing to concede this, and typically see it as an acceptable situation for abortions to occur.