Advertisement

You're more likely to start your period on a Thursday or Friday – this is why

It’s that time of the month again – you’ve got up, gone to the loo and found that familiar streak of blood in your knickers. With that familiar sign of your period having started, you may find yourself sighing and reaching for your tampons (or whatever period product you prefer).

If you track your monthly cycle religiously, you may have spotted some regularities in your period – right down to the very day you can expect to start menstruating.

And now, fascinating new research has shown that for the majority of menstruating individuals, your period is far more likely to start on Thursday or Friday compared to any other day of the week. By contrast, Tuesday is when you’re least likely to start your period.

The study, which was conducted by the Natural Cycles research team, looked at over 300,000 menstrual cycles from a total of European and North American women aged 18–40 years.

The research was done to see if the menstrual cycle bore any relationship to the lunar cycle, with some experts claiming that the moon cycles affect our sleep and therefore, can be used to predict when your period will come.

However, the results of the study suggest that actually, there are other factors at play that impact when your period will start.

a person reaching for sanitary towel
Liudmila Chernetska - Getty Images

According to Dr. Jack Pearson, Medical Affairs Manager at Natural Cycles, when your body starts to menstruate depends on lifestyle factors, such as patterns of sleep, diet and stress. These factors tend to be more dysregulated at the beginning of the week (eg: getting the Monday morning blues, worrying about work, perhaps altering your diet to perk yourself up?), compared to the end of the week, when the weekend approaches.

This hypothesis has been backed up by previous studies that have suggested that raised levels of stress can result in poorer sleep, triggering higher levels of cortisol, which interferes with reproductive hormones that determine when your period comes.

So no, your period suddenly starting on a Friday night is not your body’s way of trying to ruin your wild weekend; it could all be down to you feeling more relaxed, sleeping better and eating healthier as the week progresses.

The study also found this pattern of late week menstruation is more prominent for women with normal length or longer cycles (28 days+), and was less applicable to those with shorter cycles.

You can read the paper in full here.

You Might Also Like