Key facts about Endometriosis

Next week is Endometriosis Awareness Week (2-9th March) so we thought it would be a useful exercise to educate the Cycler community about the condition so you all know what to look out and are able to can keep a check on your health.

First, let’s start with the basics. Your endometrium is the lining of blood that builds up on the uterine walls every cycle due to your bodies natural hormonal changes. If no egg implants into the endometrium, it will break down and become your period. However, if it is fertilised, the endometrium grows thicker and protects and nourishes the growing foetus.

Healthy reproductive anatomy

Healthy reproductive anatomy


What is Endometriosis?

Endometriosis is where the lining of blood is also found outside your uterus. Areas that are most commonly involved are your ovaries, bowel or the tissue lining your pelvis.




During the menstruation stage of your cycle, endometriosis cells react similarly to your healthy endometrial cells because hormones also stimulate them to grow, break down and bleed. This therefore causes internal bleeding that can lead to irritation, inflammation, pain, and the formation of scar tissue (adhesions).  Learn more here.


Key facts:

  • 10% of women worldwide have endometriosis – that’s 176 million worldwide (Ref. 1)
  • The prevalence of endometriosis in women with infertility be as high as to 30–50%.2 (Ref. 2)
  • On average it takes 7.5 years from onset of symptoms to get a diagnosis. (Ref. 3)
  • The cause of endometriosis is unknown.
  • Currently, there is no way of preventing endometriosis but there are ways of managing symptoms and the disease.



Symptoms of endometriosis vary during the menstrual cycle, where they are often worse on the days before and during your period.

Endometriosis symptoms include:

Screen Shot 2015-02-26 at 15.26.18

Figure sourced from Endometriosis UK


If you have a combination of these symptoms it is important that you book an appointment with your GP for a check-up right away.




  1. Rogers PA, D’Hooghe TM, Fazleabas A, et al. Priorities for endometriosis research: recommendations from an international consensus workshop. Reprod Sci 2009;16(4):335-46.
  1. Meuleman C, Vandenabeele B, Fieuws S, Spiessens C, Timmerman D, D’Hooghe T. High prevalence of endometriosis in infertile women with normal ovulation and normospermic partners. Fertil Steril 2009;92(1):68-74.
  2. Diagnosis Survey. Endometriosis UK. February 2011.



Test your knowledge: are you a NaturalCycles pro?

Today is an exciting day as we now have more than half a million days of data from all our Cyclers! This means we have been able to apply this knowledge to making the algorithm even better at adapting to your specific cycle and isolating the fertile window. Hurray!


We thought a great way to celebrate this time point would be to see how Natural Cycles has helped women understand their bodies better. Aside from improving women’s health, one of our main priorities is to better educate the public about fertility so that women are able to make more informed decisions about their choice of contraception.



So here are some questions with varying levels of difficulty to see where you stand on the fertility whizz chart.  Are you a Pro Cycler or Novice?


  1. For how many days in total are women fertile throughout their cycle?
  2. How long can sperm survive within a woman’s body?
  3. What causes your resting temperature to rise after ovulation?
  4. When is the best time to measure your resting temperature (BBT)?
  5. What name is given to the phase in your cycle when you are mostly fertile?
  6. Can you get pregnant if you have sex on your period?













  1. Up to 6 days when you take sperm survival into consideration.
  2. Up to 6 days too. Did we catch you out? 😉
  3. A surge in progesterone that is associated with the start of the luteal phase.
  4. First thing in the morning before getting out of bed.
  5. The follicular phase. This is when you have the fewest green days because it is before ovulation. The luteal phase is post-ovulation and before your period starts.
  6. It’s not likely, but it can happen, especially if a woman’s menstrual cycle is short. In a 20-day cycle, for example, ovulation could occur on day 8 of her cycle then her period would begin on Day 1 and last for about 5 days. However, as you know (or have just learnt) a man’s sperm can survive in a woman’s body for up to 6 days. This means that if a couple has unprotected sex during her period then the sperm still has a chance to fertilise the egg and cause pregnancy.


Things you need to know about LH tests!

Do you have irregular cycles? Or have you just quit the pill? You might want to combine measuring your temperature with LH tests that are now from our webshop:


What is LH and why test for it?

LH stands for Luteinizing Hormone and appears for about 48 hours and is shortly followed by ovulation. You can read more here if you are interested in the science of fertility.

If you have irregular cycles then we highly recommend testing for LH. If you have recently been on hormonal contraception, it is likely that your cycle will be out of balance and irregular for up to a year. This is very individual and is taken into account by NaturalCycles’ clever algorithm, which will be even more cautious if this is the case.

It is not necessary to test LH if you do not want to, but it is a powerful supplement to the basal body temperature to indicate when ovulation has occurred. Temperature measurements have day-to-day fluctuations, which can make it challenging to identify the exact ovulation day quickly – the more data entered the easier it becomes! However, positive LH tests can help speed things up and give you more green days quicker.


2. How do I know when to test for LH?

As a woman’s LH surge happens just before ovulation, NaturalCycles will recommend that you to check LH levels a couple of days before the expected ovulation. How far in advance you need to start testing depends on how regular your cycles are.

Depending on whether you use the website or the app, the LH reminder looks a bit different. On the website, you can hover over the calendar with your mouse and you’ll see a reminder in red, for instance on the day before predicted ovulation. On both the website and the app, you’ll see “LH” with an arrow pointing at the day of the week that you should measure on, and you will also see that the the LH field will be pre-opened on the ‘add data’ window.  Additionally, on the app you will see a “Today!” notification next to the LH entry field for the day that you should test on.




Or in the app:




Please get in touch if you have questions about LH or anything else!
Have a nice thursday!

Lots of Love

NaturalCycles Team


5 things you didn’t know about sperm!

 A sperm can survive up to 5 days inside the female body under the right conditions!
That’s something we all knew about. Or did we?
Here are 5 other things about sperm that you might find interesting!

1. Some like it hot, sperm like it cold.

Temperature can lower sperm count! It is shown that men have less sperm during summer season and more during winter season. Testicles are also few degrees colder than the rest of the body.


2.  Sperm can only swim forward!

It only takes 1 sperm cell to fertilize womans body but there are approximately 200 million sperm cells per ejaculation.
Only 1 in 5 sperm will start swimming in “the right” direction after ejaculation.


3. How long does sperms cell live inside a mans body if not ejaculated?

Sperms takes weeks to mature in the body, and 1000 are made per second!  Pretty amazing right?
The sperms that are not ejaculated are resorbed by the body.


4.  Sperm have bodyguards.

Only 5% of semen contains sperm,  and a sperm only carry half as much DNA as other cells in the male body. This make it suspicious to the immune system and it therefore sees sperm as a foreign invader. The sperms bodyguards are cells in the semen that protects sperm cells, creating a barrier from immune system cells which would attack them.


5. Size does not matter.


Sperm cells are about 0,05 milimeters and can not be seen with the naked eye, unlike a human egg which is about 30 times bigger and large enough to be seen with your own eyes.



To learn more about sperm survival, visit the link and learn more about preventing pregnancy with NaturalCycles on our website!

Happy Wednesday!


learnmore startyourfreetrial







Red day Facts

A common question we often get from new users is: “Why do I have so many red days? Am I always fertile?”

The answer is of course, no! No woman is fertile for more than 6 days per cycle. The fertile window starts 5 days before ovulation (because sperm survival is ~ 5days) and ends after ovulation.

Before NaturalCycles can pinpoint your 6 day fertile window it has to first get to know what is normal for you. After all, every women is unique.



So what else can influence your number of green days?

Quitting the pill

Women who quit the pill (or other hormonal contraceptives) and switch to NaturalCycles question the number of red days they get at the start. Why? This is because hormonal contraceptives disturb a woman’s normal menstrual cycle, thus leaving women with irregular cycles until the synthetic hormones leave their bodies, and this can take several months. NaturalCycles takes this into account, giving more red days until things start to get back to normal.

Measuring and fluctuations

Another important factor to consider is, how and when you measure your temperature. We advise you to avoid measuring when you are sick, feeling hangover or if you wake up much later/earlier than usual. You can read more about measuring and basal thermometer here


Your temperature varies from day to day, but more considerable fluctuations can occur during ill or hungover days. These fluctuations in temperature can resemble ovulation or otherwise, which means NaturalCycles will give you a red ‘fertile’ day just to be safe. If you think this has happened to you then please get in touch at and we can take a look at your data and remove the anomaly that might be tainting how your cycles look.

So with this in mind, please don’t loose hope as green days are just around the corner. The more data you enter, the better NaturalCycles can pinpoint your fertile window, giving you green days in return. Have a look at this happy cycle:


To find out your fertile window and ovulation day faster, we also recommend taking an LH-test. A surge in LH hormones occur two days before ovulation and marks your most fertile days. NaturalCycles let’s you know when to check your LH levels, which also depends on how regular your cycles are. Have a look below to see what our reminders look like:


















So to sum-up – don’t worry, because green days are ahead! Just make sure you keep measuring everyday!


keep calm naturalcycles