Actually, a normal menstrual cycle can vary from about 24-36 days. And not only do cycles vary substantially among women, they often vary within each individual woman. One of the most unfortunate results of this myth is the needless anxiety that it causes women desiring to avoid pregnancy, who are led to believe over and over again that they may be pregnant because their periods are “late.”

The perpetuation of this belief is related, in part, to people’s perception of the perfect Pill cycle (boy, that’s a mouthful of p’s!). What people often do not understand is that oral contraceptives, by definition, hormonally manipulate the woman’s cycle to be a perfect 28 days. This belief in the perfect cycle is probably less widely accepted among women who have never been on the Pill.