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Understanding Your Menstrual Cycle

Understanding Your Menstrual Cycle

This article will explain the menstrual cycle in a simple way, helping you to understand the changes that occurring to your body during this time.

What is the menstrual cycle?

There are four main phases of the menstrual cycle — the menstruation phase, follicular phase, ovulation phase, and luteal phase. These phases are correlated between each other.

Ovulation occurs when a mature egg is released by the ovaries and pushed into the fallopian tube and onto the uterus. A woman is most fertile during this phase. It occurs about once a month.

The body prepares for the egg to be fertilised by thickening the lining of the uterus. It does so to create a welcoming environment for the egg to develop into an embryo. If the egg is not fertilised, the body will shed this lining before another egg arrives. This is the process of menstruation (also called a period). The body will release blood, cells, and mucus from the uterus for 3 to 7 days.

The length of the menstrual cycle matters greatly when it comes to fertilization.1 Girls and young women will experience menstruation every 21 to 45 days. Older women will experience it every 21 to 34 days (28 days on average).2 

Other factors that can cause irregular periods include stress, weight changes, emotional disturbances, and excess physical activity.3

What happens during each phase of the menstrual cycle?

Stage 1: Menstruation

The first day of your period is also the first day of your menstrual cycle and you can think of menstruation as a process of renewal. It begins with the lining of the uterus breaking down and being discarded through the vagina. This is what is responsible for the blood and mucus that is produced during your period. Once the lining is discarded, the body will begin creating a new lining with fresh cells, ready for the next egg.

On average, a woman will produce between 50 to 100 ml of menstrual fluid when they have their period.4 The rate of menstrual flow also varies between different women. Some women experience light flow at the start of menstruation, while others experience a heavy flow initially that gradually eases off.

The colour of menstrual blood also varies between individuals and changes throughout the menstrual phase.5 It is often bright red, dark red, pink, brown, and black.

Most women and girls have a menstruation phase that lasts between 3 to 7 days. You might experience some cramping and mild discomfort that can be treated with home remedies and painkillers. For the relief of period pain you could take Ponstan, a non-steroidal anti-inflammatory drug (NSAID) which reduces period pain by reducing your body’s production of prostaglandins (responsible for causing muscle cramps causing period pain).

Stage 2: Follicular Phase

During this phase, the follicles in the ovary grow. Once the lining of the uterus has been discarded, the body will begin to create a new egg and prepare for its arrival!

The pituitary gland will begin to release a follicle-stimulating hormone (FSH) that helps develop 10 to 20 follicles in the ovaries6. Follicles are cells that contain immature eggs, called ova.7 Oestrogen levels increase, which causes the lining of the uterus to become thicker. This prepares the uterus for the reception of a fertilised egg.

In most cases, only one follicle will produce a mature egg. The other follicles will be re-absorbed by the body.8 This phase begins at the end of menstruation and ends at ovulation.

Stage 3: Ovulation Phase

Ovulation occurs when a mature egg is released from the ovary.9 The egg is pushed from the ovary into the fallopian tubes and into the uterus. The lining of the uterus has thickened after menstruation and will be ready to receive a fertilised egg.  If the egg is not fertilised, it will be shed the next time you menstruate.

A complex chemical reaction occurs within the body before the egg is released.  High levels of oestrogen during the follicular phase cause gonadotropin-releasing hormone (GnRH) to be produced by the brain.10 Increased levels of GnRH cause the pituitary gland to release luteinising hormone (LH) and trigger the release of the egg.

During this time, the mucus produced by the cervix will change.  It will become slippery, clear, and elastic. This is called fertile mucus, because it improves your chances of pregnancy. Normally, cervical mucus will be thicker and opaque. The position of the cervix will also change at this time and it will become wider.

Ovulation usually occurs between 12 to 16 days before your period.11 That means a woman with a 28-day cycle will probably ovulate somewhere between day 12 and day 16 of their menstrual cycle.

The egg will survive for up to 24 hours after ovulation. Sperm will survive for up to 5 days within the vagina during the ovulation phase, assisted by fertile mucus.12 

Stage 4: The Luteal Phase

During the Luteal Phase, the follicle that released the egg begins to release the hormones progesterone and oestrogen.<13 These hormones help to thicken the uterine lining and prepare it for pregnancy. The follicle is now called the corpus luteum.14 Once the luteal phase is complete, it all starts again!

Why is important to understand your menstrual cycle?

Understanding your menstrual cycle will give you some excellent insight into your overall health. You will be able to track changes to your reproductive system, identify any irregularities and bring them to the attention of your GP as soon as possible (if required).

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