Why does menstruation occur twice a month?
Jun 01, 2021
Source: Cainiu Health
Dr. Yan Ying
Introduction
1. Ovulation bleeding—This is a normal physiological phenomenon caused by follicular rupture and a sudden drop in estrogen levels, leading to breakthrough endometrial bleeding.
2. Functional uterine bleeding—Irregular vaginal bleeding resulting from ovarian dysfunction.
3. Contact bleeding—Minor vaginal bleeding occurring after sexual intercourse, gynecological examination, or straining during defecation.
The typical menstrual cycle for women lasts 28–30 days, with most experiencing one period per month. However, a small number of women experience two periods within a single month. So, what causes menstruation to occur twice in one month? Below, we provide an explanation.
Causes of Two Periods Within One Month
1. Ovulation Bleeding
If vaginal bleeding occurs approximately 10 days after the end of the menstrual cycle—i.e., around mid-cycle—it is often associated with “ovulation bleeding.” This is a normal physiological phenomenon caused by follicular rupture and a sudden drop in estrogen levels, leading to breakthrough bleeding from the endometrium. Typically, such bleeding lasts only 3–5 days and stops spontaneously. Occasional episodes are considered normal; however, recurrent occurrences warrant medical attention and prompt evaluation.
2. Dysfunctional Uterine Bleeding (DUB)
Dysfunctional uterine bleeding refers to irregular vaginal bleeding resulting from ovarian dysfunction and is clinically abbreviated as “DUB.” Key features include menstrual irregularity, menorrhagia (excessively heavy flow), and prolonged menstruation. In severe cases, women may experience irregular vaginal bleeding—for example, two episodes of bleeding within one menstrual cycle. DUB is broadly classified into two types: anovulatory and ovulatory, with the anovulatory type being most common—particularly among adolescents and perimenopausal women.
3. Contact Bleeding
Contact bleeding refers to light vaginal bleeding occurring after sexual intercourse, gynecological examination, or straining during bowel movements—sometimes mimicking two periods within one month. Clinically, contact bleeding is commonly associated with gynecological conditions such as vaginitis, cervical polyps, endometrial cancer, or cervical cancer. Given its potential association with malignancy, contact bleeding must be taken seriously. Prompt cytological testing (e.g., Pap smear) or cancer screening is essential to rule out malignancy.
Above are the primary causes of experiencing two menstrual periods within one month. We hope this information is helpful to you.
