Soung Yung- kuei, chairman of OBGYN at Chang Geng Memorial Hospital, explains that in an agricultural society a woman's menstrual cycle begins relatively late. Add to this relatively early marriages and frequent, closely spaced births, and these factors greatly reduced the number of menstrual periods a woman had in a lifetime, which naturally reduced the possibility for cells in the inside membrane of the uterus to shift position.
長庚醫院婦產科主任宋永魁解釋，在農業社會婦女來潮較晚，加上早婚、生育次數多而密集，因此一生中月經次數相形減少，子宮內膜細胞發生異位的機會自然也少。