What actually is a period?

Let's revisit the biology of the menstrual cycle...
06 October 2020

Interview with 

Caroline Overton, Royal Society of Obstetricians and Gynaecologists


a graphic of female reproductive system


It’s October, and now that kids are back at school here in the UK, perhaps it’s time to consider some conversations other than covid that might be taking place in the corridors, classrooms and bathrooms. This year in England the government announced it was making period products freely available for schools to order in, for kids that need them. And according to period.org, the 10th October marks national period day in the US. So this week we are pondering periods. How does the menstrual cycle work, and change throughout life? When should you seek help if you’re worried about your periods? And how can we improve access to not just period products, but period education too? First though, what actually is a period? Close to half the global population have them each month - but how confident are you of the basics? Consultant gynaecologist Caroline Overton is with us to get us all up to speed. But first, here are Eva Higginbotham and Phil Sansom with a quick fire science...

Eva- If you have ovaries and are between the ages of about 12 and about 50,   chances are that roughly each month you’ll experience a period - a bleed from the vagina. It’s not dangerous, or gross. It’s biology.

Phil - Periods are unique to the person having them, but on average, they tend to start at around 12 years of age and will last somewhere around 5 days each time.

Eva - Say a typical menstrual cycle is 28 days long. Day 1 is the first bleeding day, and by day 5 or so the bleeding will have  probably stopped. A few weeks later, day 14 or so, the brain will release chemical messengers - called hormones - into the bloodstream that tell the ovaries to release an egg into the adjoining fallopian tube. Then the ovaries release hormones to thicken the lining of the uterus (sometimes called the womb), in case the released egg meets a sperm on it’s way down the fallopian tube and gets fertilised.

Phil - The egg - fertilised or not - then moves into the now thickly lined uterus. And if it’s not been fertilised, it breaks down.

Eva - Ovarian hormone production drops, and the uterus lining also breaks down, and it’s the broken down lining that comes out of your vagina for a few days that is your period.

Katie - Caroline, which hormones were Eva and Phil talking about there?

Caroline - Oestrogen and progesterone, produced by the ovaries and controlled by the pituitary gland.

Katie - So those are the main hormones we're talking about when we're thinking about the cycle, is that right?

Caroline - Those are the main hormones.

Katie - When we talk about blood loss - and we'll talk about pain in a little bit as well - is it possible to quantify how much bleeding we're talking about, and how much pain people might experience? Is there a typical amount?

Caroline - So a typical amount of blood shouldn't make you an anaemic. You shouldn't be passing big clots; you might pass tiny clots, but you shouldn't pass clots bigger than a 50p. And essentially you should be able to carry out your work, school, normal activities, without needing to stay at home. In terms of pain, you might need to take a household painkiller such as paracetamol or ibuprofen, but it would be abnormal to regularly miss work, school, or activities because of period pain.

Katie - So we heard there, around the ages of between about 12 and 50 is when people would tend to menstruate. People who have ovaries are born with potentially millions of eggs in the ovaries, is that right? So why do we actually stop menstruating?

Caroline - We don't know exactly why people stop menstruating. We know that there are still eggs present in the ovaries, so there is some sort of signal for the periods to cease; exactly why, we don't know.

Adam - When that actually happens, it's called the menopause. So what actually goes on then during that, in the body?

Caroline - Menopause just means "end of periods". Actually, what happens... there are greater changes happening in what we call the perimenopause, the run up to your periods stopping. And there, your periods - which might've been regular and monthly - start to first of all get closer together, so they're coming around maybe twice in a month; and then they will tend to space out, you'll start to miss periods, and you might also start to get the symptoms of low oestrogen of which hot flashes and night sweats are the classic ones.

Adam - We associate periods with fertility. So what happens if that menopause happens much earlier than expected?

Caroline - So you're quite right that some women can have an early menopause before the age of 40. It is commoner in some families, so it's worth asking if your mother had an early menopause; sometimes it's the result of surgical or hormonal or chemical treatments, for example for cancer.

Adam - What should women do if they run into these problems?

Caroline - I think the main thing is to be aware that your periods are a sort of marker of your hormonal wellbeing; you should have them roughly monthly, and if your periods have suddenly changed to stop, then there's something not quite right. Women shouldn't feel embarrassed to go along and talk to their GP and say that their periods have changed.

Adam - How serious would it be, or is it just something that just needs to be dealt with?

Caroline - It would all depend on the stage of life. Early menopause is going to be very serious if somebody is still planning to have a family, but mostly people with ovaries will have spacing out periods due to hormone imbalances like PCOS, which I think we're going to discuss later. And all of this is amenable to treatment.


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