What is Menstruation?

Menstruation, also known as a period, is the monthly discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina in women of reproductive age. The length of each woman's menstrual cycle varies; it can also change throughout life. Menstrual cycles are often irregular prior to your 20th birthday or after your 40th, as you approach menopause. Your period is at its most regular between the ages of 25 and 35. Stress and illness can also affect your cycle.

The menstrual cycle

The menstrual cycle lasts an average of 28 days. The cycle starts on the first day of menstruation and consists of three phases:
  • The follicular phase (day 1 through day 13)
  • The ovulation phase (the 14th day)
  • The luteal phase (day 14 through day 28)

Cycle length and duration can differ from person to person. So do not worry if your cycle is longer or shorter than the average 28 days.

What happens during the menstrual cycle?

Each month, your body prepares itself for a possible pregnancy. Under the influence of the hormone estrogen, the egg cells mature and an extra thick layer of mucus forms in the uterus. An egg cell is released (ovulation) approximately 10 days after the last menstruation. Levels of the hormone progesterone now increase considerably to protect the egg cell. If the egg cell is fertilised by a sperm, it then embeds itself in the lining of the uterus. If no fertilisation takes place, then hormone levels decrease and your body rejects the extra uterine lining, usually around 14 days after ovulation. This takes the form of blood and mucosal tissue discharge, your menstruation. Your period usually lasts between two and seven days.

Symptoms related to your menstrual cycle

Approximately 75-85% of women experience unpleasant physical or psychological symptoms before or during their menstruation. 1,2 You are not alone! Physical complaints include abdominal or uterine cramps (dysmenorrhea) , back pain, extreme blood loss (menorrhagia), tiredness and fatigue related to blood loss, weight gain, constipation, breast tenderness and headache. 3 The most common psychological symptoms are: mood swings, irritability, anger, crying, oversensitivity, feeling nervous and anxiety.1,2

Prevalent physical complaints Common psychological and emotional complaints

Premenstrual syndrome (PMS)

It is very common for women to suffer a spectrum of complaints in the days leading up to their period. Also known as premenstrual syndrome (PMS) is the name given to the physical, psychological and behavioural symptoms that can occur in the two weeks before a woman’s monthly period. There are many different symptoms, but typical examples are: breast pain, bloating, mood swings and irritability. These symptoms usually decrease or end once your period starts. Women often describe this as ‘like a fog lifting’.

Intra-cyclic bleeding (vaginal bleeding between periods)

You may sometimes bleed between menstruations. This is usually nothing to worry about and is often caused by fluctuations in hormone levels or triggered by taking certain medicines. However, blood loss between your periods can have a different cause: an inflammation of the cervix due to an STD (sexually transmitted disease), for example. So if you experience intra-cyclic bleeding, it is always best to get it checked by your physician to put your mind at rest.


1. Yonkers, K. A., O’Brien, P. M. S. & Eriksson, E. Premenstrual syndrome. Lancet (London, England) 371, 1200–10 (2008).
2. Naeimi, N. The Prevalence and Symptoms of Premenstrual Syndrome under Examination. J. Biosci. Med. 3, 1–8 (2015).
3. Menstruation, menopause, and mental health | womenshealth.gov. at https://www.womenshealth.gov/mental-health/menstruation-menopause/

Related: Expert advice for a comfortable menstruation