The Adia Blog

Stories about our journey, our members, and useful information about fertility.

Is period syncing a myth?

This question has been on the Adia team’s mind recently. As a team, we spend a lot of time talking about periods, and all things women’s reproductive health. Nothing is too taboo for our office chat! For the past few months Lina and I have synced up perfectly. Lina is still breastfeeding, and so had been having pretty irregular periods, and I’ve only just started having periods again having changed my contraception. But since I’ve started my period, Lina’s cycle is now perfectly tracking mine – which is pretty handy, but also has driven a debate as to whether there is any science behind it.

This isn’t the first time I’ve experienced period syncing – there’s been university housemates, other close work colleagues, school friends – the list is pretty exhaustive. And it seems too precise to just be coincidence, or is it?

In recent years science has been skeptical that period syncing is a thing. A recent study by Oxford University and the period tracker Clue –  thought to be the largest of its kind – has found data showing women’s periods do not synchronise when they live together after all. They followed 360 pairs of women. Analysing three consecutive cycles in each pair, the research found the vast majority – 273 pairs – had a greater difference in period start dates at the end of the study than at the beginning!

But talk to any woman and they will likely tell a similar story. Google it and the internet is full of similar stories. The idea actually started with research findings published in Nature, a scientific journal, in 1971. A researcher called Martha McClintock studied the menstrual cycles of 135 women in an American college.  She found that the onset of the date of menstruation was more similar among friends and roommates than among random pairings of women

The most prevalent theory was that it was an evolved strategy among females to co-operate with each other – to stop becoming a kind of harem for a single dominant man. The idea is that if women had synchronised cycles, they would all be fertile at the same time – so one man would not be able to reproduce with them all. A form of biological sisterhood.

It’s clear that science doesn’t back up these theories – yet, at least. And perhaps we are just looking for patterns where they don’t exist, but a theory of synchrony, collaboration and sisterhood is certainly more interesting.

To understand more about your reproductive health, Adia offers easy finger-prick hormone blood tests and short questionnaires. Find out more about our Hormone Tests here.

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