Five myths about menstruation

Samantha Wild
Clinical Lead for Women's Health and Bupa GP
27 February 2024
Next review due February 2027

Periods are a normal part of life, and there’s lots of information about the menstrual cycle available. But there are some common misconceptions about periods that may be misleading. Here, I share five myths about menstruation, and explain whether there’s any truth behind them.

two people laughing in a group

You can't get pregnant during your period

You’re most likely to get pregnant if you have unprotected sex around the time that you ovulate. Ovulation usually happens around 10 to 16 days before your period starts. But if you have unprotected sex when you’re on your period, there’s still a chance you could get pregnant.

This is because you could ovulate soon after the end of your period if you have a short menstrual cycle. Or if you have irregular periods, it might be hard to track when ovulation happens. Sperm can survive in your body for five days, so fertilisation could happen in the days after you have sex.

If you want to avoid getting pregnant, it’s best to use contraception at all times in your cycle, including during your period.

Your menstrual cycle can synchronise with others

The idea that your menstrual cycle could ‘sync up’ with the cycles of others was first suggested by a 1971 study. This study proposed that chemical signals called pheromones were responsible.

More recent studies haven’t found any clear evidence that syncing occurs.

Experts think that ‘syncing’ is more likely due to chance. Period and cycle lengths differ between people, so with time, menstrual cycles may naturally overlap.

It's unsafe to skip your period using the pill

If you take the contraceptive pill you’ll usually take one pill a day for 21 days, then take no pills for 7 days. Or instead you may take an inactive pill that contains no hormones over the 7 days. Then you’ll start taking active pills again for 21 days, repeating the cycle. During the 7-day break in hormones, you’ll have a bleed.

A common misconception is that this bleed is a natural period. But it’s actually a withdrawal bleed that happens due to the change in hormone levels.

Some people choose to skip the withdrawal bleed using the pill. This is done by continuing to take active pills, rather than having a 7-day break. Research has shown that avoiding this withdrawal bleed is safe, and won’t affect your future fertility. There’s also no blood ‘building up’ inside your womb if you choose to do this.

One thing to consider though, is that taking the pill without a break may not stop bleeding entirely. Some breakthrough bleeding or spotting might still occur. If you find that bleeding continues, you could try another method to manage your periods. Ask your doctor for advice.

You can’t go swimming on your period

During your period, it’s fine to swim and do other forms of exercise. Gentle exercise when you’re on your period can also help to reduce period pain. But you may worry about your blood leaking into the water. Or you may be unsure about which period products are suitable to swim with.

If you’d like to swim on your period, it’s safe to use a tampon or menstrual cup. There’s also waterproof period swimwear that you can try. It’s unlikely that leakage will occur, but if any does by accident, it’s okay. Period blood won’t contaminate swimming pool water.

If you have irregular or heavy periods there’s something wrong

If your period is irregular, it may happen more or less often than a typical cycle of 24 to 38 days. Or it may be unpredictable. Signs of a heavy period include:

  • changing your pad or tampon very often
  • bleeding through your clothes
  • needing to use two sanitary products at the same time
  • passing large blood clots

Heavy bleeding may also stop you from carrying out your usual activities, such as working or going out.

Everyone’s period is different. Irregular or heavy periods  may sometimes happen due to factors like increased stress or contraception. Your periods are more likely to be irregular when they first start during puberty, and when you’re close to menopause.

But for some people, irregular or heavy periods could be a sign of a health problem. If you’re ever worried about your periods, it’s important to speak to a doctor about what you’re experiencing. Whatever the issue, help is available if you need it.

If you have heavy, painful, or irregular periods, you’ll know just how disruptive they can be, both physically and mentally. With our Period Plan, you don’t have to face these problems alone.

Samantha Wild
Dr Samantha Wild
Clinical Lead for Women's Health and Bupa GP



Atiya Henry, Health Content Editor at Bupa UK

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