Unborn Baby Experiences Pain 8 Weeks After Conception
"The neural circuitry responsible for the most primitive response to pain, the spinal reflex, is in place by 8 weeks of development. This is the earliest point at which the fetus experiences pain in any capacity. And a fetus responds just as humans at later stages of development respond, by withdrawing from the painful stimulus."
Maureen L. Condic, Ph.D., University of Utah, School of Medicine, Department of Neurobiology and Anatomy, before the Subcommittee on the Constitution and Civil Justice, Committee on the Judiciary, U.S. House of Representatives, 23 May 2013
This Congressional hearing took place prior to the U.S. House of Representatives passing the "Pain Capable Unborn Child Protection Act" which would ban abortions after 20 weeks (with narrow exceptions) in all 50 states. Full testimony: http://judiciary.house.gov/hearings/113th/05232013/Condic%2005232013.pdf