ABORTION/CASEY ANTHONY

I have been following the case of Casey Anthony and I am reminded of Susan Smith and Andrea Yates.  They may have suffered from a psych disorder when they committed atrocities against their children, but I don't understand why any of these mothers have been persecuted for taking their children's lives after birth.  No one takes offense if they act before birth.  Isn't a life a life?  Aren't we guaranteed the "right to life, liberty, and the pursuit of happiness" in our constitution?  I had understood these "rights" are guaranteed as long as they don't infringe upon other's rights.  What am I missing?  As long as abortion is legal AND the taxpayer supports this industry with our tax dollars, leave these mothers alone!  Either murder is wrong or our lives are protected under the constitution.  Which is it?  Stop trying to have it both ways!