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Do you remember having Sex Ed at school and you were told that you could get pregnant at any time? Or maybe you had an accident and rushed to get the morning after pill because any unprotected sex pretty much leads to pregnancy, right?

Well if you were told any of the above you may be surprised to know that we are actually only fertile for a few days each month. If this is shocking news to you, then please do read on as all will be revealed.

Let's Talk About The Menstrual Cycle

I did a post on the menstrual cycle a while back but let's talk about it from the fertility point of view, and remember the key is that they body wants the sperm there ready for ovulation so it meets the egg before it becomes unviable. Those little guys have quite a journey including being put into suspended animation and having to navigate the fallopian tubes/mazes.

After your period, or a couple of days after your period starts, your follicles start to mature in your ovary. As they do this they produce estradiol (a type of oestrogen) that triggers other processes to help with fertility. Firstly, it triggers the growth of the uterine lining so the egg has something warm and nourishing to implant in until a placenta is grown.

It also triggers a few other processes as well such as cervical mucus/fluid production and different types of fluid appear throughout your cycle. Your cervical fluid has many functions including filtering out defective sperm, providing swimming lanes to propel healthy sperm upwards faster and to nourish and protect the sperm on their journey.

You may well have noticed fluid in your panties and assumed it was some kind of discharge thinking it was an infection or self cleaning. This is often your cervical fluid and it is a sign of fertility. You produce it in the lead up to ovulation to get sperm into the right place and keep it healthy until ovulation occurs.

In a typical 28 day cycle you may see period, then a few dry days then fluid, starting off thick and opaque and gradually becoming more slippery, wet and transparent. This may overlap with your period in shorter cycles. However, this is the start of your fertile window and the start of your fertile time, even though you haven't ovulated yet.


This is the big even our body is gearing up to, the release of the egg from the ovarian follicle and collection by the fallopian tube. This actually only takes around 15 minutes but we often say this phase is 3 days long. This is because your egg is viable for 12-24 hours after it has been released and, within a day of that happening the ovary could also release an egg (double ovulation aka non identical twins), which will also last 12-24 hours.

Also during ovulation, the follicle that housed the egg before it was released transforms into something called the corpus luteum which produces progesterone. Progesterone is pretty awesome, it matures your womb lining and tells the body to heat up so it can act as an incubator for your possibly fertilised egg.

What is even more amazing, is that you can tell when your body is producing progesterone to sustain this by measuring your basal body temperature (your temperature on waking first thing in the morning). That window until your progesterone has really taken over is the period in which you can still get pregnant.

Once your body has cranked up the progesterone production (and you can see a thermal shift on your chart), you can no longer release any more eggs and you enter the luteal phase.

The luteal phase lasts approximately 2 weeks before your hormone levels drop off and you start your period (or not if you are pregnant). Once we know you are in established luteal phase, you are no longer fertile.

So What Does That Mean For Fertility?

Well let's say you have a 28 day cycle, you have a period and possibly a few dry days. Then you enter your fertile window for the 5-6 days before ovulation (approximately). Then you are fertile for a few days after ovulation. So you are likely to only be fertile for around 8 days a month. That is 20 days of non fertile time.

Is This The Case For Everyone?

Unfortunately not, there are a few caveats. Teenagers, whose cycles have yet to normalise will have irregular ovulations and bleeds. The same is true for women who are on the pill (or any other hormonal contraceptive), severely ill, post partum, have irregular cycles or entering the menopause.

However, if they learn to chart their cycles using one of the Sympto-Thermal Methods (STM) such as Fertility Awareness (FAM) or Natural Family Planning (NFP) under the guidance of a teacher and you will start to see what your body is doing on the inside, even when on the outside it feels like your body has a mind of its own.

Learning More

This isn't enough knowledge for you to prevent pregnancy but you can learn more about Natural Family Planning or Fertility Awareness from a qualified teacher such as myself. (I have a course teaching you how to chart the signs here). You can actually learn your fertility status by charting your body's signs and symptoms throughout the month. Pretty cool, hey?

Find Out More

Find out more about your hormones

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