"The highest density of pain receptors per square inch of skin in human development occurs in utero from 20 to 30 weeks gestation. During this period, the epidermis is still very thin, leaving nerve fibers closer to the surface of the skin than in older neonates and adult…Thus, a fetus at 20-32 weeks of gestation would experience a much more intense pain than older infants or children or adults…"

[expert testimony provided to the Northern District of the US District Court in CA (15Apr04), Dr. Sunny Anand (Dir, Pain Neurobiology Lab, Arkansas Children's Hospital Research), emphasis added]