I personally detest the modern scientific thought-frame that its just "a clump of cells". That terminology seems Orwellian to me, and is a slippery slope to quickly dehumanize the subject.
I'm in favor of a choice to abort in special circumstances such as rape or mental defects, but then again that simply opens the door to more loosely defined slopes. Its like...where do we draw the line? Its either 100% yes or 100% no.
I'm 100% behind having the choice to abort. Even though I dunno if I could have my partner go through with it.
I've had several friends get abortions and it's a very difficult and traumatic experience. None of them ever got a second one. It's not like some have portrayed as a common and easy form of birth control.
Whatever reasons they had, it boiled down to not being able to provide for the child one way or another.