How the menstrual cycle works

The menstrual cycle, how long it lasts and what causes its abnormalities. Here’s everything you need to know about your period and menstruation


The menstrual cycle marks the biological clock of women and is an important component of their psychological and physical well-being. Knowing your cycle and understanding how it works allows you to feel good about yourself and to be aware of which are the fertile days to get pregnant , the reasons why the menstrual cycle can be irregular and everything that revolves around the cycle and the menstruation .

The first menstrual cycle and menopause

The first menstrual cycle is called menarche (first appearance of menstruation): it occurs between the ages of 10 and 16. Before the age of 10 we speak of precocious puberty , the non-occurrence of menstruation over the age of 18 is called primary amenorrhea. Menopause (definitive cessation of menstruation): occurs on average around the age of 50. When menstruation ceases before the age of 45 we speak of premature menopause , if it ceases after the age of 55 of late menopause.

Here is everything you need to know about the menstrual cycle , its possible irregularities, anomalies, its phases.

Menstrual cycle length

The duration of the menstrual cycle is the time interval between the first day of a period and the first day of the next period. The duration can be variable. A period ranging from 25 to 31 days is considered normal, with an average of 28 days. There are those who consider the limits of normality more broadly, extending them over a period ranging from 21 to 36 days.

Stages of the menstrual cycle

The cycle is divided into two phases :

  • first phase (preovulatory, or proliferative, or follicular, or estrogenic phase)
  • second phase (postovulatory, or secretory, or luteal or progestin phase).

Menstrual cycle symptoms

In some women, the cycle occurs only with blood loss lasting from three to five days and does not present any particular discomfort or symptoms. In other women, however, the cycle involves symptoms such as abdominal pain, breast tension, headache, back and joint pain, fatigue and sleepiness. Irritability and bad mood can also be closely linked to hormonal fluctuations associated with the menstrual cycle.

Menstrual cycle calculation

How often does the menstrual cycle come ? Every month all women of childbearing age find themselves wanting (or having) to calculate the days that have passed since the last cycle to understand if there is a delay or some anomaly, such as an early menstrual cycle or too short or too long duration . In women who have a regular cycle, it is enough to calculate about 28 days from the last cycle to understand when it is likely to recur. 

But not all of them have such a regular rhythm. It is useful to listen to your body and be able to interpret the symptoms that may herald the onset of your period. Usually ovulationit is the event that separates the two phases of the menstrual cycle. In case of irregular cycles or long cycles , while the duration of the first phase (preovulatory) is variable, the duration of the second phase (postovulatory or luteal) usually has an average duration of 12-16 days. 

To women who are wondering if you can get pregnant right after your period or during your period, you have to answer that yes, it is possible for this to happen. Normally, in women who have a regular cycle of 28 days, the days in which ovulation occurs are the central ones, which means that during and after menstruation they are not fertile. 

But if the cycle is shorter ovulation can also occur immediately after the period or even during and this means that there is always the possibility of a conception.

What has been described so far concerns the normal characteristics of the menstrual cycle.

Irregular menstrual cycle

Sometimes irregularities in the menstrual cycle can occur, here are the main causes of these alterations:

  •  Amenorrhea

complete absence of menstruation for at least 3 months. In a woman’s life, the absence of menstruation is physiological only in the following periods: infancy, pregnancy and lactation, menopause. The absence of menstruation can also be the most important and significant symptom of an early pregnancy, especially if your period has always been regular and you have had intercourse during the fertile period.

  •  Polymenorrhea

menstruation excessively close together, that is, they occur with an interval of less than 25 days (short cycles, with close flows);

  •  Oligomenorrhea

menstruation occurs at intervals of more than 36 days;

  •  Hypomenorrhea

poorer than normal menstrual flows;

  •  Hypermenorrhea

heavy menstrual flows;

  •  Menorrhagia

excessively profuse menstrual blood loss, haemorrhagic, for a longer duration;

  •  Metroraggia

blood loss of varying degrees that occurs independently of the menstrual period, or in a period when there should be no menstruation (pregnancy, postmenopause or before puberty);

  •  Menometroraggia

blood loss that began with menstruation and persisted for several days even after the menstrual period;

  •  Dysmenorrhea

particularly painful menstruation.

Menstrual cycle delay

If the period does not occur and is late, the first thing to check is that there is no pregnancy in progress. The causes that can lead to a delay or absence of the cycle are:

  •  pregnancy
  •  ovarian cysts which can also cause white or brown discharge after your period or irregular menstruation
  •  hormonal dysfunctions that cause periods to skip
  •  stress, medications and other factors