The embryonic period lasts from implantation until about the 8th week of pregnancy. (Ornstein, Robert, PhD. The Roots of the Self. p. 36. NY: HarperCollins Publishing, 1995.)

By the eighth week, the fetus will kick when poked. (Karr-Morse, Robin, and Meredith S. Wiley. Ghosts from the Nursery. p 52. NY: Atlantic Monthly Press, 1997.)

By the eight week, the brain has developed its three parts. (Ratey, John J., MD. A User’s Guide to the Brain. p 23. NY:Vintage Books, 2002.)

By seven and a half to eight weeks the fetus is able to experience sensation when reflex responses to somatic stimuli begin. (Derbyshire, Stuart W. G., PhD. The Science and Politics of Fetal Pain.)