How do you measure that line?
That's a good question, and the answer is probably best left to people with a much better understanding of neurobiology etc. I do tend to err on the side of sentience, though. If there are scientific questions as to whether a baby in the womb is sentient or not at a certain point in its development, I would not allow abortion at that point. However, if there is no argument that the baby, at that particular point, is sentient (such as 72 hours after conception) I have no problems with terminating the pregnancy.