With Roe v. Wade, the U.S. Supreme Court gave states the right to legislate abortion restrictions during a woman's second trimester. Many states enacted laws that make it more difficult to terminate a pregnancy. Among them, Arkansas, Minnesota, and Georgia require physicians to tell women that 20-week-old fetuses can feel pain during the procedure unless they are anesthetized. A newly released review of the scientific evidence, however, suggests the premise of those laws is wrong.
Fetuses cannot feel pain until at least the 28th week of gestation because they haven't formed the necessary nerve pathways, says Mark Rosen, an obstetrical anesthesiologist at the University of California at San Francisco. He and his colleagues determined that until the third trimester, "the wiring at the point where you feel pain, such as the skin, doesn't reach the emotional part where you feel pain, in the brain." Although fetuses start forming pain receptors eight weeks into development, the thalamus, the part of the brain that routes information to other areas, doesn't form for 20 more weeks. Without the thalamus, Rosen says, no information can reach the cortex for processing.
