Your Menstrual Cycle - What exactly happens?

 
 
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Everything You Need to Know About the Menstrual Cycle…

We all have a vivid memory of our first period, don’t we? We bet the first time was daunting for you as it is for most of us. No matter how prepared you are, the sight of blood coming out of your body is something that needs getting accustomed to. And, oh boy – do we get accustomed!

This cyclic blood loss every month marks the beginning of a love-hate story called the menstrual cycle. The menstrual cycle is a structural and hormonal change in our reproductive system that prepares us for pregnancy. Normally it is around 28 days but this can be highly variable from person to person.

Every month a single (or sometimes multiple!) egg is released halfway through the cycle. If the sperm finds an egg to fertilize then this is when you become pregnant. If that does not happen, the egg – along with the lining of the uterus – gets shed in the form of a period (or menses).

The female body is an anatomical masterpiece and the menstrual cycle is proof of that. The cycle works in multiple phases and can be described by either change in the ovary or in the uterus – both of which occur simultaneously. Stay informed of your body’s physiology - keep reading to learn everything you need to know about the menstrual cycle!

The Uterine Cycle - What happens to our uterus during mensuration?

The uterine cycle explains the changes that happen in the uterus throughout the menstrual cycle. Here’s how we divide the uterine cycle:

1.     Menstruation

2.    Proliferative Phase

3.    Secretory Phase

Menstruation

The active loss of blood or menstruation is the initial stage. This makes day 0 of the uterine cycle. Menstruation is caused by the shedding of the thickened uterine wall and release of certain pain mediators like prostaglandins that cause the classic period cramping in the first few days of menstruation. On average, we lose about 35 ml of blood in each cycle wit menstruation usually lasts anywhere from 3 to 7 days.

Proliferative Phase

The next stage in the uterine cycle is the proliferative stage. This is when the recently shed uterine walls begin to develop again. The size of the walls begins to thicken again under the influence of estrogen. The proliferative stage lasts for about 14 days when the secretory phase takes over.

Secretory Phase

As the name implies, the secretory stage is when the uterus begins its secretory functions, develops ducts and has a tremendous increase in blood flow. All of these changes are attributed majorly by the circulating progesterone in the blood during this time.

If pregnancy does not occur, the lining of the uterus sheds in the form of menstruation and the cycle repeats.

The Ovarian Cycle - What Happens to Egg During the Menstrual Cycle?

Another way to describe what happens in a menstrual cycle is through the ovarian cycle and its stages. The ovarian cycle mirrors the different stages of a developing egg and is the key to enable us to  track ovulation and assess your fertility status.

The changes in the primary female hormones – estrogen, progesterone, FSH and LH – are what dominate the ovarian cycle. These hormones not only play a role in the changes in the ovarian cycle but also have a major hand in the changing moods throughout the cycle. So next time you wonder what’s got you down right before your period, science has an answer for you!

The different phases of the ovarian cycle are:

1.     Menstruation

2.     Follicular Phase

3.     Ovulation

4.     Luteal Phase

Menstruation

There’s a lot of overlap between the ovarian and the uterine cycle. Both cycles begin with menstruation as the first stage where the egg is released and the uterine lining is shed. This is when the hormones are at their lowest levels in the blood. This explains the low moods that many women experience at the beginning of their period.

Interestingly enough, studies show that a good proportion of women feel the most aroused during this time as well. The exact mechanism of an increased libido during your period is still under scrutiny but it could be because of the increased levels of testosterone – the designated male hormone! But let’s not digress – whatever the cause of the libido surge is, we’re not complaining!

Follicular Phase

Moving on, the next two weeks in the ovarian cycle are called the follicular phase where the egg increases in size in the ovary thanks to the high level of estrogen and FSH (follicle-stimulating hormone).

Ovulation

Day 14 is when the egg is released from the ovaries as a result of an acute rise in LH (luteinizing hormone), high estrogen levels and rising progesterone. This is when you’re at your highest fertility level, best mood, and an increased (logical!) libido. So if you’re planning to start a family, ovulation is the time you want to look out for.

Luteal Phase

Luteal phase follows ovulation and lasts for 2 weeks. Progesterone and LH levels are high during this timeframe and they continue to rise if pregnancy occurs. The end of the luteal phase is when we suffer from the dreaded ‘pre-menstrual syndrome’ or PMS. The declining level of hormones is what causes a mood shift, increased appetite and an overall feeling of being ‘down’.

If the egg remains unfertilized then the cycle repeats with menstruation.

So What Happens to the Cycle When You Get Pregnant?

We’ve already established that if fertilization doesn’t take place, the egg is released, the uterus sheds and the cycle repeats. But what if you did get pregnant, what then?

Well, then the fertilized egg implants in the developing uterus. The remaining cells of the egg form a structure called the corpus luteum that continues to secrete progesterone for the uterus. This acts as a source of nutrition for the implanted fertilized egg until the placenta is well developed and ready to take over.

The menstrual cycle ceases after fertilization and remains in the secretory phase. The cycles continue as normal a few months after the delivery of the baby.

How Can I Track My Menstrual Cycle?

Whether you’re trying to get pregnant or trying not to, either way tracking your menstrual cycle will do you good. Fertility tracking is a historical method of contraception and it’s still being used widely today. Although not entirely accurate, you can still have a good idea when you’re at your more fertile period.

There are several period tracking apps available now for phones. These apps work by simple mathematics and determine when you’re most likely to ovulate according to your individual menstrual cycle.

Many of these period tracking apps do make the mistake of telling you that you are fertile on certain days, however this may not be true! The only way to conclusively tell if you are fertile is through biological tests (check out our blog post on the topic here).

The Bottom Line…

Learning how your body changes throughout the menstrual cycle can give you a good insight when you’re planning to start a family. Menstrual irregularities are also fairly common. If you notice a problem with your normal cycle, it’s a good idea to check in with your doctor.

 

Sources:

https://www.healthline.com/health/womens-health/stages-of-menstrual-cycle

https://www.webmd.com/baby/charting-your-fertility-cycle#1

https://www.ncbi.nlm.nih.gov/books/NBK279054/

https://www.healthline.com/health/how-long-does-your-period-last

Chantelle Bell