Image by Tina Tiller
Image by Tina Tiller

ScienceJuly 19, 2022

Everything you ever wanted to know about periods, part one

Image by Tina Tiller
Image by Tina Tiller

You asked us all your period questions and we took them to the experts. Today: the nuts and bolts of bleeding and busting some myths. 

All week we are examining our relationship with menstruation in Aotearoa. Read more Bleed Week content here. 

If there’s one thing we’ve learned in researching for Bleed Week, it’s that everyone learned about periods in a different way. Some had a book left on their pillow from a period fairy, others had a tampon dunked in a glass of water in front of their class. Some relied entirely on Dolly Doctor and urban legends shared at sleepovers, and others never got taught anything at all. 

So we put the question out there – “what do you want to know about periods but have always been afraid to ask?” – and took your inquiries to a panel of experts across the country. 

What is the appropriate and most inclusive language to use around periods these days? 

You may have noticed we haven’t been gendering periods during Bleed Week, and there is a good reason for that. “Referring to ‘people with periods’ or ‘people who menstruate’ is both more accurate and inclusive than using gendered terminology,” explains Claire Black, general manager at rainbow support organisation Outline. “There are many people who menstruate who are not women. This can encompass transmasculine people, including trans men, as well as some non-binary people, some intersex people, and other gender-diverse people.”

I am a person with a period swimming in the ocean. Can a shark smell me? 

“This is an old wives’ tale,” says Clinton Duffy, leading shark expert at DOC. While sharks have an extremely sensitive sense of smell that can detect one part of blood per million of water, this is only one sense that sharks use to navigate and find food. “A shark in the immediate vicinity of a swimmer may be able to detect minute traces of blood, but they would have already been alerted by the vibrations and sounds associated with swimming,” he explains. 

There is also a question of motivation – Duffy has dumped 40-50kg of minced fish into the sea and waited hours for sharks to show up (and sometimes they don’t at all). “Like most predators, sharks are typically cautious animals and do not generally rush in and bite the first object they come across,” he explains. “Finally, sharks do not usually view humans as prey hence the very low incidence of shark attacks, particularly here in New Zealand.” 

This shark is not interested in your period (Photo: RNZ)

OK well, if the sharks won’t bite then I will: what… is… a period? 

“A period is the body’s normal response to not becoming pregnant,” says Michelle Wise, deputy head of obstetrics and gynaecology at the University of Auckland. “Every month the lining on the inside of your womb builds up getting ready for a fertilised egg to implant. If the body recognises that your hormones have changed and are indicating that you are not pregnant, then all of that extra lining just sheds and sloughs away, and that’s what you see as your period.” 

Jane Girling, associate professor in the department of anatomy at the University of Otago, explains that this lining is known as the endometrium. “If the pregnancy doesn’t occur, then the endometrium will start to break down… The tissue and blood then exit the body via the cervix and the vagina. In the meantime, the endometrium repairs and the whole cycle begins again. It is remarkable to think this happens throughout an individual’s reproductive years.”

How much blood do you lose on average during a period?

Dr Claire Henry, research fellow in Otago University’s obstetrics department, says the key thing to emphasise is that everyone’s flow is different. “For someone with a ‘normal’ period, that is, bleeding around for around five days and changing a pad/tampon every four or so hours, the average blood loss per cycle is around 30ml,” she explains, comparing it to three tablespoons or a shot glass. “But people can lose less than that, or up to around 80ml in a cycle. 80ml or more may suggest heavy bleeding, which is an important symptom to have checked.” 

How much blood can I lose over a lifetime? No don’t tell me! No do!

Henry did some maths on this one for us. “If a person has a regular ‘normal’ menstrual cycle (ie 12 periods a year), and has their period from 14 to 50 years old, they will have had approximately 430 periods. 430 periods at 30ml each equals approximately 13 litres in a whole lifetime.” However, she encourages people not to think about it as “losing” blood. “Your body regenerates the lining of the uterus after each period, and with each cycle it will fall away again.” 

It’s actually fine (Photo: YouTube)

Is it OK to donate blood while I am bleeding or is that simply too much blood leaving too many places?

“There’s no problem with donating blood while you’re menstruating if you’re in good health,” says a spokesperson from the NZ Blood Service. “While it’s true that you do lose a little iron with your period (0.5mg of iron per ml of blood lost), this should not be a problem if you are getting enough iron in your diet.” All NZ Blood donors have their haemoglobin levels checked before donation and they’ll let you know if your levels are looking too low to donate. If you have missed your period, you may be asked to rule out pregnancy before you donate to avoid any stresses on you or your baby’s circulation, or iron levels. 

What are the most common period symptoms? 

“Discomfort or pain with menstrual periods is really common and can start from your very first period,” says Girling. “Some people also experience other symptoms like bloating, back or leg pain, headaches and bowel symptoms.” Those bowel symptoms, or what an inquirer referred to as “bad guts”, are extremely common, elaborates Wise. “Gastrointestinal side effects are the effect of prostaglandin hormones, those are the ones that cause the nausea, the vomiting, the loose stools, the diarrhoea.” 

Mood swings are common too. “Your oestrogens and your progesterones are the hormones that cause the shift in your mood,” says Wise. “A lot of people describe mood symptoms when they get their period, some people get headaches, some people get all of that prior to their period, some get it during their period. “It’s really interesting how much variation there is in people’s symptoms, but anything cyclical they can track.” 

‘ bleedweek ’
Calum Henderson
— Production editor

If there is so much variation in symptoms, how do we know what is abnormal? 

“This is a great question,” says Henry. “It can be hard to tell what is normal/abnormal, and everyone is different.” Abnormal period symptoms can include bleeding longer than seven days and bleeding between cycles, heavy periods (changing tampon/pad hourly, or the presence of clots), short or very light periods not caused by contraception, severely painful periods, bleeding after sexual intercourse and post-menopausal bleeding.

“Periods shouldn’t interfere with normal life too much,” she explains. “Another way to think of it is – is this disrupting my work, school or personal life? Is this having an impact on my mental health?” Wise agrees. “If pain or other symptoms start interfering with your daily life, then it is time to go and get some help.” If you do believe your periods are abnormal, it is important that you make an appointment with your health provider, GP or Family Planning clinic. 

Tampons, a panty liner and a sanitary napkin from different manufacturers are on one table.
These things shouldn’t rule ya life (Photo: Getty Images)

What is the cramping pain, where is it coming from, and why won’t it stop? 

Imagine the uterus as a giant, muscly organ, says Wise. “That huge strong muscle layer is basically contracting down while the body is trying to get rid of that thickened lining to start again for the following cycle.” Another source of the cramping is that all the tiny little arteries in the uterus are squeezing shut when you have your period. “By cramping down those little arteries it is stopping the blood flow, so it is our bodies’ natural physiological way of stopping ourselves haemorrhaging. It’s actually quite amazing.”

How does endometriosis affect period pain? 

“Endometriosis is a chronic inflammatory condition where tissue resembling the lining of the uterus is found in other areas it shouldn’t be,” says Henry. “Because of this, endometriosis can cause severely painful periods, or sometimes increases the length of periods.” Other symptoms of endometriosis include infertility, tiredness, pain during intercourse or painful bowel movements.

“It can be hard to diagnose endometriosis for reasons at the healthcare provider, system and biological level,” explains Henry. “If you are suffering these symptoms and they are having an impact on your social, personal and mental wellbeing, please seek care and advocate for yourself for a specialist gynaecology appointment. The Endometriosis New Zealand website is fantastic for getting a better idea of what’s normal and what is abnormal.” 

This all sounds quite annoying. Why doesn’t the body just reabsorb the blood?

“This is a really, really, interesting question because most mammals don’t actually have a menstrual cycle, they have what is called an estrous cycle,” says Girling. During an estrous cycle, the endometrium (lining) remodels for a possible pregnancy, but doesn’t have the same tissue breakdown AKA the bleeding. 

Wait, so you’re telling me that other animals don’t have periods like we do? 

“Humans are actually extremely unusual in having a menstrual cycle.” Girling explains. “Only some of the other primates, like chimpanzees and gorillas, also have menstrual cycles.” Along with primates, there are a few species of bat, the elephant shrew and the spiny mouse who also menstruate. All we can say for sure is: this brings a whole new meaning to the term mouse pad. 

Read part two here – featuring contraception, bleeding after birth and the “menstrual chaos” of menopause.


Keep going!
Image by Tina Tiller and Archi Banal
Image by Tina Tiller and Archi Banal

ScienceJuly 19, 2022

Siouxsie Wiles: What Covid-19 and vaccines do to our periods

Image by Tina Tiller and Archi Banal
Image by Tina Tiller and Archi Banal

Covid-19 and vaccinations have both shown to affect menstruation, but there’s a real lack of interest in studying it, writes Siouxsie Wiles.

All week we are examining our relationship with menstruation in Aotearoa. Read more Bleed Week content here. 

As soon as the Covid-19 vaccines started rolling out overseas, people began posting on social media that they were experiencing changes in their periods. Some were bleeding early, others late. Some had a heavier flow, others a lighter one.

Medical experts were quick to say it was probably nothing, while the anti-vaxxer wellness influencers and disinformation agents used these anecdotes to spread fear about the safety of the vaccines. All we really knew at that point was that those designing and running the clinical trials hadn’t included any questions about whether people experienced changes to their menstrual cycle or bleeding in the days/weeks/months after they were vaccinated. It’s hardly surprising. Menstrual-related conditions and women’s health, not to mention trans and non-binary peoples’ health, have long been neglected by doctors, researchers and the funders of medical research.

So, more than two years into the pandemic, what do we now know about the impact of Covid-19 infections and vaccines on periods?

Before I answer that question, let’s do a quick menstruation 101. Menstruation is the shedding of the uterus lining if someone doesn’t get pregnant. It happens on a roughly monthly basis, but the number of days people bleed each cycle, how heavily they bleed and the length of their actual cycle, varies between people. It can even vary in the same person over time. The menstrual cycle is controlled by a mixture of hormones regulated by the hypothalamus, pituitary gland, and ovaries, also known as the HPG axis (the G stands for gonadal if you’re curious). Anything that impacts the body and disrupts the HPG axis can impact a person’s menstrual cycle. Stress, heavy exercise and extreme dieting are all known menstrual cycle disruptors.

Covid vaccines and menstruation

In April 2021, Dr Kate Clancy, Dr Katharine Lee and their colleagues launched a survey using social media asking people to report their experiences of menstrual bleeding after getting a Covid-19 vaccine. They’ve just published the results from their first three months of data collection. They excluded people who’d had Covid-19 because of its potential impact on menstruation. We’ll get to that later. They also excluded anyone 45-55 years old because they didn’t want menstrual changes related to perimenopause to confound their results. That left them with data from over 39,000 people.

So, what did they find? Of those people who normally had a period, 42.1% reported a heavier flow after being vaccinated. A similar proportion, 43.6%, reported no change. The results are similar to a smaller Norwegian study of 5,688 women aged 18-30 years which also found heavier bleeding to be common after vaccination. In Lee and Clancy’s study, those who experienced heavier bleeding were more likely to be older, Hispanic/Latinx, have experienced fever and/or fatigue after being vaccinated, have a lighter typical menstrual flow, have been pregnant and/or have given birth. People with endometriosis, menorrhagia (bleeding for more than a week), fibroids, and polycystic ovary syndrome (PCOS) were also slightly more likely to experience heavier bleeding.

Another study took advantage of an existing dataset from a menstrual cycle tracking app to look at whether vaccination impacted the timing of people’s menstrual cycles. Of the 3,959 people in the study, 2,403 of them were vaccinated. The data showed that having their first vaccine dose didn’t change the timing of their next period, but the second dose delayed it by half a day on average. For the people most affected, their cycle length changed by as much as 8 days, which is considered clinically significant. The good news is that cycle lengths returned to normal two cycles after vaccination.

I think one of the most important aspects of the new study by Lee and Clancy and colleagues is that they also included people who didn’t normally have a period, either because they’ve been through menopause, use long-acting reversible contraceptives/continuous hormonal contraceptives, or receive gender-affirming treatment that suppresses menstruation. Many of these people experienced breakthrough bleeding after being vaccinated. As the authors point out in their discussion, not only can break-through bleeding cause unnecessary concern (unexplained vaginal bleeding is a symptom of uterine cancer in postmenopausal people), it can also have potentially life-threatening consequences. For example, unexpected bleeding can be psychologically distressing for people who experience gender dysphoria. And thanks to all the bathroom hysteria and anti-trans hatred currently being stoked, finding themselves unexpectedly bleeding while out in public has the potential to put some trans people in real physical danger.

What’s also interesting is that it turns out that menstrual cycle disruptions are likely nothing to do with the Covid-19 vaccine specifically and everything to do with just getting vaccinated. Back in 1913, Dr Albert Lamb from the Presbyterian Hospital in New York published a paper on the effects of the typhoid vaccine on menstruation in nurses at his hospital. He noted missed, late and heavier periods in vaccinated nurses. He also wrote: “Where these irregularities occur the patients are more apt to have associated with them a more troublesome general reaction.” More recently, in 2018, a Japanese study of the human papillomavirus (HPV) vaccine found vaccination was associated with an increased risk of irregular menstruation and what they called an “abnormal” amount of menstrual bleeding.

In other words, unsurprisingly, stimulating the immune system can temporarily disrupt the menstrual cycle. And as Dr Lamb noted, the bigger the immune response stimulated by the vaccine, the more likely the disruption.

Covid infection and menstruation

So, what about getting Covid-19? What impact does that have on menstruation? Well, despite more than 500 million confirmed cases of Covid-19 having been reported worldwide, there is almost no data on that.

Several studies have looked at menstruation during the pandemic but not at infection specifically. For example, one study looked at the data for 1,159 women from 15 countries who recorded their menstrual cycles during 2019 and 2020 using the fertility tracker Daysy. The researchers found that on average menstrual cycles lengthened after the pandemic began. But it appears the researchers didn’t have information on whether any of the women experienced a Covid-19 infection, so the study doesn’t tell us much. It’s a similar story with a study of users of the Natural Cycles app.  Meanwhile, a study of 263 people surveyed in May 2020 about the length of their periods, their pad use, and their anxiety. Nothing about a Covid-19 infection.

Of the studies that have looked at people with Covid-19, one was about 158 female patients in an isolation ward in Jakarta and found that more than a third reported heavy bleeding and menstrual irregularities. They also found that patients with symptoms of mental health disorders were twice as likely to report a menstrual change. Another looked at 177 confirmed Covid-19 patients hospitalised in China and found that 25% experienced changes in the amount they bled and 28% experienced changes in the length of their cycle.

‘ bleedweek ’
Alice Neville
— Deputy editor

Those were all hospital patients, so are likely to have been severely ill. What about non-hospitalised Covid-19 cases? Well, there’s a report of 127 people who are part of Arizona’s CoVHORT study which found that 16% experienced changes in their menstrual cycle. The most reported changes were irregular or infrequent periods and an increase in premenstrual symptoms. Compared with Covid-19 cases that didn’t report any changes to their periods, those that did were more likely to report having experienced more Covid-19 symptoms, including fatigue, body aches and pains, and shortness of breath. The latest study I can find is from a long Covid study of 3,762 people published last year. Interestingly, they found that many of their participants reported experiencing relapses of symptoms during or before menstruation, something that’s been reported for people with chronic fatigue syndrome.

More studies are needed!

I think we can safely say that the (published) data on the impact of Covid-19 infection on periods/the menstrual cycle is woefully lacking right now. Anyone who works in women’s health, beyond breast cancer, won’t be at all surprised. Before the pandemic, I got interested in what studies had been done on menstrual cups and was shocked to find almost nothing. This is par for the course when it comes to the health of people without penises and frankly, we should all be up in arms.

Beyond vaccination and infection, just the fact we are in a pandemic will be impacting people’s menstrual cycles. Increased stress, drinking… If you want to read more on this topic, there’s a good review article in the International Journal of Epidemiology that was published open access (so no paywall, yay!) in December 2021. Dr Gemma Sharp and colleagues have reviewed what’s been published so far and summarised the outstanding research questions. Questions like, might catching Covid-19 as a kid impact when your period starts? Are people more or less susceptible to infection at different stages of their menstrual cycle? And does hormonal therapy or contraception have an influence on Covid-19 symptoms?

Here’s hoping people are managing to get some funding to find out! Or maybe it’ll be like a lot of the long Covid studies, and we’ll have to crowdfund it ourselves.