Despite it being a bodily process that almost all women and girls, above and below a certain age, experience on a monthly basis, periods are still, unfathomably, considered a taboo.
According to a worrying new survey, many teenage girls are choosing not to participate in PE lessons at school when they are on their period.
Research conducted by Betty for Schools – an initiative striving to open up the conversation around periods in schools – found that almost half (46 per cent) of women said they had used their periods to skip a PE class.
They asked 2,000 adult women about their experiences and found that the main reason why 46 per cent of them had skipped PE when they were at school and on their period was because they were scared about leaking.
More than a third of women (39 per cent) listed the fear of leaking as their biggest reason while the second largest reason (24 per cent) was a worry that their sanitary pads would be visible to others or slip out during exercise.
Half of women also said they had experienced periods so painful and heavy that they had physically prevented them from playing sport while 63 per cent of women said they "dreaded" PE lessons if they were during their time of the month.
Just two years ago, this rang true for British tennis champion Heather Watson who said her defeat in the first round of the Australian Open came down to "girl things". This then spurred the former British tennis number one Annabel Croft to call periods "the last taboo" in sport, saying female athletes often "suffer in silence".
All in all, the majority of women surveyed (68 per cent) were in firm agreement that if girls received better education about periods and all the many ways it can affect their bodies, they would be more comfortable taking part in exercise. Preach.
Almost three in four of the women (73 per cent) said that period education also needs to stress how exercising can actually benefit girls on their period.
As all the women who were surveyed had left school, 59 per cent reflected that avoiding sports during school years can negatively impact the way women feel about physical exercise when they get older.
Sam Quek, who stormed to a gold medal victory with the Team GB women's hockey players in the Rio Olympics last year, is supporting Betty's campaign to encourage teachers and parents to talk to children more about periods and exercise.
"For me, sport and exercise are a huge part of my life," she said in a statement. "I find it really sad that periods – something all women experience for a big part of our lives – are creating a barrier to sport for so many.
"We have to work to break down taboos around periods – this starts with elite sportswomen being more open and honest, with schools creating the environment where girls can talk about the changes their bodies are going through and education that empowers us all the know and understand our bodies better."