in detail, the decision about what should be called "abortion" and what should be called "contraception" or pregnancy prevention are not agreed upon. Definitions of pregnancy beginning Traditionally, doctors have measured pregnancy from a number of convenient points, including the day of last menstruation, ovulation, fertilization, implantation and chemical detection. This has led to some confusion about the precise length of human pregnancy, as each measuring point yields a different figure. At its 2004 Annual Meeting, The American Medical Association passed a resolution in favor of making "Plan B" emergency contraception available over-the-counter, and one of the claims in the resolution was that hormonal contraception that may affect implantation "cannot terminate an established pregnancy." Similarly, the British Medical Association has defined an "established pregnancy" as beginning at implantation. The legal definition in the United Kingdom is not clear. Other definitions exist. The American Heritage Stedman's Medical Dictionary defines "pregnancy" as "from conception until birth." Definitions like this may add to a lay person's confusion, as "conception" in a scientific context may be defined as fertilization, in a medical context can mean either fertilization or implantation but in lay terms may mean both. Whether conception refers to fertilization or implantation would seemingly even impact "established pregnancies" such as an ectopic pregnancy. If conception is defined as at implantation, ectopic pregnancies could not be called pregnancies. However, some medical professionals who oppose birth control, such as Walter Larimore of the Focus on the Family group, have argued that the medical definition of conception should include fertilization. Finally, the standard historical method of counting the duration of pregnancy begins from the last menstruation and this remains common with doctors, hospitals, and medical companies. This system is convenient because it is easy to determine when the last menstrual period was, while both fertilization and implantation occur out of sight. An interesting consequence is that the dating of pregnancy measured this way begins two weeks before ovulation. Although many anti-abortion advocates have argued that both pregnancy and status of a separate human life beginning happen at fertilization, several examples also exist of people within those movements taking alternate views. For example, doctor and social activist Bernard Nathanson wrote in his 1979 work Aborting America that a confirmed moment of implantation should be considered the point at which a distinct human being exists. He specifically stated (note that 'alpha' is his shorthand for an organized group