Dispelling Period Myths: What Science Actually Says

Introduction

Menstruation has been surrounded by myth, taboo, and misinformation across cultures and centuries. These myths are not merely harmless folklore — they lead women to restrict their behaviour unnecessarily, delay seeking treatment, experience shame, and make poor health decisions. This article addresses the most persistent period myths with evidence-based clarity.

Myth 1: All Women Have 28-Day Cycles

The "28-day cycle" is a medical average that was historically reinforced by hormonal contraceptive packaging. In reality, normal cycles range from 24 to 38 days, and significant inter-individual variation is the norm. A 2019 study of 600,000 cycles (via the Clue app) found that only 13% of women had 28-day cycles; the median was 29.3 days, with the most common range being 25–30 days. Cycle length also varies with age, weight, stress, and exercise.

Myth 2: You Shouldn\'t Exercise During Your Period

Exercise during menstruation is not only safe — it can actively reduce cramps. Exercise releases endorphins, which are natural pain modulators and mood boosters. A 2018 Cochrane review found that exercise (particularly yoga and aerobic exercise) significantly reduces dysmenorrhoea severity. Light to moderate exercise is appropriate throughout the cycle; some women may find high-intensity training uncomfortable on the heaviest days, but this is personal preference, not medical necessity.

Myth 3: Menstrual Blood Is "Dirty" or Impure

Menstrual fluid consists of blood, endometrial tissue, cervical mucus, and vaginal secretions. It is not "dirty," toxic, or pathological. The myth of menstrual blood being impure or dangerous appears across many cultural traditions and has been used to exclude women from religious spaces, kitchens, and social participation. There is no scientific basis for these restrictions. Menstruation is a healthy, normal physiological process.

Myth 4: Painful Periods Are Always Normal

Mild cramping (primary dysmenorrhoea) from prostaglandin release is common and manageable with NSAIDs or heat. However, severe dysmenorrhoea — particularly pain that worsens over time, persists outside of periods, or is associated with deep pain during sex — is not "normal." These symptoms can indicate endometriosis, adenomyosis, or pelvic inflammatory disease. The normalisation of severe pain is one reason endometriosis is diagnosed an average of 7–10 years after symptom onset.

Myth 5: You Can\'t Get Pregnant During Your Period

While pregnancy during menstruation is unlikely, it is not impossible. Sperm can survive up to 5 days in the reproductive tract. If a woman has a short cycle (e.g. 21 days) and ovulates on Day 7, sperm deposited on Day 2 (during her period) could still be viable at ovulation. Women with irregular cycles are particularly at risk of this misconception. Effective contraception should be used consistently, not selectively.

Myth 6: Missing a Period Means You\'re Pregnant

Pregnancy is the most important cause of missed periods and should always be excluded first. But missed or irregular periods also commonly result from: stress (hypothalamic suppression of GnRH

Myth 7: PMS Is "All in Your Head"

Premenstrual syndrome involves real, measurable physiological changes. Brain imaging studies show altered amygdala reactivity in women with PMDD during the luteal phase. Neuroimaging and neuroendocrine research have identified changes in serotonin, GABA, and allopregnanolone systems. PMS and PMDD are recognised medical conditions by the DSM-5, ACOG, and the World Health Organization\'s ICD-11. While psychological factors influence symptom severity, the underlying biology is unequivocal.

Myth 8: You Should Not Swim or Take Baths During Your Period

Bathing, swimming, and water sports are entirely safe during menstruation. Menstrual flow is reduced or temporarily halted by water pressure during swimming. Menstrual cups, period swimwear, or tampons allow comfortable participation in water sports. Hot baths can actually soothe menstrual cramps via muscle relaxation and vasodilation.

Myth 9: Irregular Periods in Teenagers Always Normalise Without Treatment

While it is true that cycles in the first 1–3 years after menarche are often irregular as the HPO axis matures, persistent irregularity — especially cycles consistently >45 days — after age 15–16 warrants evaluation. PCOS, thyroid disease, and eating disorders are important diagnoses not to miss, all of which are treatable and have long-term health implications if left unaddressed.

References: Grieger JA et al., Clue dataset 2019; Cochrane review on exercise for dysmenorrhoea 2018; ACOG Education on Menstruation; WHO ICD-11; DSM-5 PMDD criteria.