Why are most Democrats pro-choice, but against the death penalty?

I just don't understand how a person can think it's okay to kill am innocent baby and not a convicted criminal. Sounds VERY backwards to me. And I know there are innocent people on death row, but I don't think a fetus has ever killed a person in cold blood. Democrats also use the "we shouldn't be able to choose who lives and who dies" argument for the death penalty. Why doesn't the same apply for babies? I know there are woman out there who have been raped, but I don't think it's right that some women have abortions like I eat cereal - on a regular basis. I'm not a Republican, I think all politicians are idiots. I just don't understand this backwards way of thinking. Thanks.