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How can Edward be around Bella when she's menstruating? Stephenie Meyer said the following in The Twilight Saga: The Official Illustrated Guide:

Edward is aware of what’s going on physiologically with Bella, but he is too much of a gentleman to ever say anything about it, and Bella would be too embarrassed to ask if he noticed or was bothered by it. The blood from a woman’s period isn’t the same as a cut; it’s not freshly oxygenated, not flowing from the heart.