According to healthline Period length varies from one woman to the next. Women’s menstrual periods range in length. Menstruation occurs once every 24–48 days in most women. Some women, however, have their periods twice a month instead of once. Short-cycle menstruating women are more likely to have this problem.
According to Medical News Today, endometriosis may result in more frequent menstruation than once per month. Abnormally heavy menstruation is a common symptom of endometriosis, a condition in which tissue similar to uterine tissue grows in other regions of the body.
In the years leading up to menopause, women often experience period irregularity and even period skipping. This time period is known as perimenopause. That’s why some women experience twin periods in a single cycle. Healthline says that a woman may have two periods per month if she has shorter periods due to stress, birth control pills, or an overactive or underactive thyroid.