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 for abortion and have seen the price the mother (and rest of the family) pays mentally afterwards. My wife and I were faced with the decision to end a pregnancy due to medical complications with the baby and we have both paid the price mentally for ending it early. The child would've suffered immensely duing her life even if she survived childhood and would've never been able to experience a great quality of life. Sadly the condition isn't able to be diagnosed until around 20 weeks and in most states 24 weeks is the cutoff for abortions. It was the hardest decision we have ever faced as a couple (and for me personally) and one we didn't make lightly. The majority of women who decide to abort don't make the decision lightly as a "oops I got pregnant and don't want to be" scenario like many pro-life people claim. It was the right decision for us but we still remember the child we didn't have.
I wouldn't wish the situation on anyone but I fully support the option to have one being legal.