The primary reason that we do menstrual extractions on ourselves is for training or demonstration purposes. Over the years, most menstrual extraction groups have been composed of women who either used effective birth control or who did not have regular penis-vagina sex or who were lesbians or celibate. However, no birth control method is 100% effective.
This is not to say that menstrual extraction groups only (underline “only”) perform menstrual extraction on members of their own group. A group often does this for women outside their group because they have done enough uterine size checks to know the size, shape and texture of a woman’s uterus and to come within a week or two of how far along the pregnancy is, and they’ve learned the procedure well enough that they want the experience of performing menstrual extraction on someone that may be pregnant. Then they will do it on a friend, or a friend of a friend who they can keep in touch with.
Especially, in the early days of menstrual extraction, before Roe v. Wade(underline “Roe v. Wade”), our group learned how to do uterine size checks by doing them on women who we referred to the hospital for a legal abortion. We accompanied the women through the procedure at the hospital and we saw the products of conception. This gave us immediate feedback. We realized that women could learn to estimate the length of pregnancy accurately with minimal training.