The brain circuitry for processing pain seems to be complete by 26 weeks' gestation, But true pain requires not only development of the brain but also development of the mind to accommodate the subjectivity of pain.
Your link was quite interesting, and i did want to make a point to you about it.
Of course, your "right to life" site will, make it sound that a zygote, is a baby, that is what your site is trying to do. When infact the fertilized egg, is known as a zygote, By the time a women is four weeks pregnant, the fertilized egg will have implanted itself into the uterine lining. At this point, the zygote is now known as an embryo. After implantation, the embryo begins to divide itself into two: one part of it will develop into the placenta while the other will go on to become the baby.