The Menstrual Cycle

The Menstrual Cycle


Is the menstrual cycle the same as a period? What does day 1 mean? When does ovulation happen? Am I fertile throughout the entire month? These questions and many more plagues those of us who menstruate. Unfortunately, we are often left uninformed when it comes to our cycles, apparently a topic still so shameful and taboo that it remains mostly off-limits. But we truly believe that you deserve to understand how your body works and functions. Having this information can be extremely helpful, and we hope that it will empower you to recognise when something isn't right with your own cycle and better advocate for yourself.

What is the menstrual cycle?

Nope, your period is not the menstrual cycle…it is just one part of it. You can think of the menstrual cycle as a series of processes that occur each month. It is very well-coordinated and relies on hormone signals to get your body ready each month for a potential pregnancy. We call it the menstrual cycle because menstruation (also known as a period or menses) is the act of shedding all the tissue and blood that lines the uterus (called the endometrium) if you didn’t get pregnant the previous month.

The menstrual cycle has 4 phases:

  • Menstruation
  • Follicular Phase
  • Ovulation
  • Luteal Phase

Menstruation

You can imagine that there is a little vault inside your ovaries where all your eggs are kept. You are born with all of the eggs that you will ever have and by the time you reach menopause, the end of your reproductive life, there are no eggs left that are capable of ovulating. The first phase of your menstrual cycle is called the menstrual phase – this is when you get your period because pregnancy has not occurred. The thickened lining of the uterus, which generally would help to support a pregnancy, is therefore not needed. A combination of blood, mucus, and tissue from your uterus is shed through the cervix and vagina. The duration of the menstrual phase can be anywhere between 2 to 7 days.

Follicular phase

What is known as the follicular phase starts on the first day of your period (it overlaps with the menstrual phase) and ends when you ovulate. It begins when a group of eggs are released from the vault, your ovaries – which is referred to as a “cohort”. Each egg resides in a follicle, a fluid-filled structure. In our brain, we have a gland called the hypothalamus, which you can think of kinda like the hormonal control centre. This produces a hormone known as gonadotropin-releasing hormone, GrNh for short, which stimulates another gland in the brain called the pituitary gland. The pituitary gland produces follicle-stimulating hormone, also called FSH. The hormone FSH is appropriately named as it stimulates follicles (and the eggs inside them) to grow. One lucky egg (known as the dominant follicle) will be chosen to mature in preparation for ovulation and the other eggs will die away (although in some cases, there can be two or more eggs that mature – hence twins).

As the dominant follicle (egg) continues to grow, it produces a hormone called estrogen. Estrogen is what stimulates the lining of the uterus to thicken in preparation for a potential pregnancy. Once estrogen levels reach a certain level, it signals to the brain that the egg is at maturity and is ready to be released. The hypothalamus then uses GrNh to communicate this to the pituitary gland. The pituitary gland responds by releasing a surge of LH, luteinizing hormone.

Ovulation

The LH surge is what triggers the egg to be released, known as ovulation, from the follicle ready to be captured by the fallopian tube. That egg then travels down the fallopian tube toward the uterus to be fertilised by sperm. The ovulation phase is the only time during your menstrual cycle that you can become pregnant (yes, really!).

Luteal phase

After the egg has been released, the remaining follicle then forms a new structure called a corpus luteum. The corpus luteum makes progesterone which is essential to prepare the uterus for pregnancy. If you do get pregnant, the pregnancy makes the hormone HCG (which is what you test for in pregnancy tests) and the corpus luteum actually remains active and helps by continuing to produce progesterone until the placenta is fully formed and can take over (which occurs around 9 weeks into pregnancy).

If no pregnancy occurs, then the corpus luteum dies. It can only live around 14 days, so after this, if you are not pregnant, it dies away. Your progesterone levels drop, which signals to your body that there was no pregnancy this month. That drop in progesterone tells the uterus to bleed. That is your period. While that is happening, the next group of eggs is getting ready and the brain is going to send out FSH again, to get the process to repeat.

How long is the menstrual cycle?

You might have heard people talking about the length of their cycle being perhaps 21 days, 24 days, 30 days and so on. But what exactly are they talking about? Well, the beginning of the menstrual cycle is the first day of your period or day 1. This starts the first half of the cycle that we call the follicular phase. We then keep counting the days until the day before the start of your next menstrual bleed. This is what we consider your menstrual cycle length. A “normal” menstrual cycle typically ranges from 21-35 days, however, each person should have a narrower range of what is normal for them. Meaning that maybe one month the length of your menstrual cycle is 24 days and the next month it might be 25.

Irregular menstrual cycles and what causes them

An irregular menstrual cycle is when the length of time between periods varies or the duration of the period itself is different each month. It can be caused by factors such as stress, weight changes, certain medications, or underlying health conditions. It's not unusual to have the odd wonky month, and this is not a reason to rush to the doctor. It is also normal for menstrual cycles to be irregular during certain times in a person's life, such as the onset of menstruation, the transition to menopause, the use of hormonal birth control, and post-pregnancy. However, if your periods have been repeatedly irregular or even absent, don't ignore them! Finding out why can help prevent many short and long-term health implications and provide peace of mind.

Tracking the menstrual cycle

Ever heard of menstrual cycle tracking? It can be a complete game changer in helping you to better understand your body, predict when your period is coming (period products handy anyone?) and identify irregularities in your cycle. You can think of it as a powerful tool for tuning into your body’s rhythms and promoting self awareness. And who doesn’t love feeling in control and empowered? Give it a try, there are plenty of free period tracking apps available, you might even surprise yourself with just how much you learn about yourself and your body.

Key points on the menstrual cycle

  • Your period is part of one bigger cycle called the menstrual cycle
  • The menstrual cycle involves the brain, the ovaries and the uterus and it involves a set of processes controlled by hormones
  • The menstrual cycle length is counted from the first day of bleeding (your period) to the day before your next bleed
  • Age of first period (menarche) 10-15 years
  • Menstrual blood flow for 2-7 days
  • The menstrual cycle is not always perfectly predictable.
  • Ovulation typically occurs around day 14 of a 28-day cycle, but can vary depending on the individual and the length of their cycle.
  • Menstrual blood flow can range from light to heavy and can vary from cycle to cycle.
  • Hormonal changes during the menstrual cycle can result in symptoms for some menstruators such as cramping, bloating, and mood changes.