Firstly, your dates are wrong. See above. Secondly, drawing an arbitrary line is all we can do in this issue, or else accept the only arbitrary line drawn by nature, which is birth. Even the arbitrary line of conception is not available to us because it is undetectable. Besides neither conception no birth are satisfactory in any way in terms of social responsibility or practicality. Thirdly, science, or at least biology, is not on the business of allowing or disallowing. Science allows the Holocaust, nuclear weapons, amputation and euthanasia. It's societies that decide how science should be used, based on what is scientifically possible and understood. This, if society determines, as you do that the appropriate time to stop abortions is just before the foetus feels pain, then science tells us that point is between 20 and 24 weeks . If society prefers to go with a detectable foetal heartbeat, six weeks is the limit. The decision is not made by science, it is informed by science.