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Hertility’s menstrual cycle basics: Periods 101

Periods 101
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Hertility’s menstrual cycle basics: Periods 101

Whether it's creating bleach-free & plastic-free period care products or breaking down period related taboos & stigma, here at Mooncup, we're kickstarting the menstrual health revolution. 

As part of Hertility’s commitment to making knowledge about reproductive health the norm, they’ve created this 5 part blog series called Menstrual Cycle Basics for the &SISTERS community, kicking off with what actually happens when you’re on your period. Let’s dive right in. 

People often confuse the menstrual cycle and period, but are they the same thing? No, they aren’t! A period is only the first part of your menstrual cycle (when you bleed) whereas a menstrual cycle describes the length of time between the first days of two consecutive periods.


Exclusive offer!
Check-in on your menstrual health today with Hertility's at-home Hormone & Fertility test, using code SISTER10 at checkout to get £10 off. 

Why do we even get periods? 

With every menstrual cycle, your body prepares your uterus to be a nice comfortable home to support a potential pregnancy. Even if this isn’t remotely on your radar, your body won’t have got the memo.

Through the cycle, the inner lining of the uterus (called the endometrium) will keep building up as an egg is maturing in the ovaries. This happens with the help of important hormones that control your cycles called oestrogen and progesterone. Oestrogen helps the eggs to grow and mature and, along with progesterone, helps the endometrial lining to become thick to be ready to receive a fertilised egg.

If you get pregnant, the endometrium is where the embryo attaches to and gets its nutrition. But if there is no sperm-meet-egg moment (and therefore no fertilisation), it causes oestrogen and progesterone levels to drop. This is what triggers the endometrium to break down because the body no longer needs it. 

This lining gets shed along with blood through the vagina during your period. For this to happen, the uterus contracts with a little help from prostaglandin - this is why you might get cramps during your period. As your period comes to an end, the endometrium will start to build up and thicken once again.

How long should periods last?

On average, periods last for 3-5 days, but anything between 2 and 7 days is considered normal. You’ll usually notice that the first two days are the heaviest.  

Menstrual cycles (remember that’s the time between the first days of 2 consecutive periods) should usually last between 21 and 35 days. Although it’s a common belief that cycles last for 28 days, in fact only 10 to 15% of us have cycles that last this long. If you have cycles that are shorter than 21 days or longer than 35 days, they would count as irregular, even if you have periods eg: every 40 days on the dot. 

The length of your cycles and therefore your periods can also change from time to time because it’s easily influenced by factors like stress, diet, exercise, sleep and medication.

It is common for periods to be irregular when you first start getting them as you go through puberty as well as when you’re about to stop getting them around the time of menopause. The length of your cycles and therefore your periods can also change from time to time because it’s easily influenced by factors like stress, diet, exercise, sleep and medication. But consistently irregular cycles could be a sign of underlying health conditions such as PCOS, premature ovarian insufficiency (POI) and hormonal imbalances influencing thyroid, oestrogen or testosterone levels. 


Your periods are the pulse of your reproductive health. Take Hertility’s online health assessment to combine details of your periods with your medical history, lifestyle and any symptoms you’re experiencing to create a personalised hormone test to figure out if anything is going on (or going wrong) with your reproductive health. Don't forget to use code SISTER10 at checkout to get £10 off.

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