How To Track Your Fertile Window
When you first start trying for a baby, you assume that you have sex and (fingers crossed) get pregnant. You know generally how long your cycle is, and you have an idea of when you ovulate, so you try to plan sex around that time. Maybe you even start using ovulation tests and time sex for the day you ovulate. But you’re still not pregnant, and you don’t know why. It could be that you are actually missing your most fertile days. And this is why you need to track your fertile window.
The fertile window is the few days in your cycle where you are most likely (but not guaranteed) to get pregnant.
This is because your fertile window is the 4 to 5 days before you ovulate and the day of ovulation.
Once you ovulate, the egg is only viable for approximately 24 hours after it is released. That is not a very big window. Did you also know that sperm can live inside your uterus for up to 5 days! 5 days! By having sex in the days before you ovulate, you can ensure that you have a healthy supply of sperm already to meet the egg once it has been released.
It is important to know when your fertile window is so that you can time sex accurately and maximise your chances of getting pregnant.
Experts recommend that you have sex every 2-3 days throughout your cycle to give yourself the best chance of getting pregnant.
However, what about the people who have a low libido? Or the people that have a demanding job or lifestyle? What about the couples that already have children and don’t have the time to have sex every few nights. Or the couples have been trying to conceive for some time and having sex every few days hasn’t worked yet, and they just need a bit of a break from the constant sex. For these people having sex every few days can be unrealistic or exhausting.
When I was trying to conceive I Google and researched everything, and I’m going to share that information with you in this post. Keep reading to find out how to track your fertile window.
Please note – I am not a medical expert. This post is based on my personal experiences and research. Everyone will have different experiences and results. Always contact a medical professional for advice.

Know Your Cycle
Sounds obvious, but it’s so important to know your menstrual cycle! Anything from 21 to 40 days is considered a normal cycle. If you’re not sure of yours, it’s easy to work out. You just need to count from the first day of your last period to the day before your next period. The first day of your period is the first day of a full flow. Spotting does not count as CD1 (cycle day 1).
It’s worth tracking your period for a few months so that you can work out what exactly is normal for you. The added bonus of tracking your cycle also means that you can prepare for your period by stocking up on reusable pads, paracetamol, and your favourite treats.
For me, trying to track when I was fertile felt like an impossible task because my cycles vary from 28 – 45 days each cycle!
Cervical Mucus (CM)
Also called cervical fluid. I know it sounds unpleasant BUT, it’s one of the easiest ways to track your fertile window. CM is the fluid or gel-like discharge that comes from your cervix. During your monthly cycle, your body will produce different types of CM. This is due to your hormones doing their business.
Depending on where you are in your cycle, CM will either be preventing the sperm from reaching your uterus, or it will be helping them reach your uterus.
CM goes through 4 different stages throughout your cycle;
- Dry or sticky – Usually, the few days after your period has finished
- Creamy – Not fertile yet
- Wet or watery – Ovulation is coming
- Wet and stretchy, also called EWCM (egg white Cervical Mucus) – This is the most fertile type of CM and means it’s time to get jiggy with it!
Some experts suggest sticking a finger up there to find out what is going on (with clean hands, obviously!) However, I don’t think that’s necessary, do you? Just having a little peek in your underwear or when you wipe should be fine, but do whatever you are comfortable with!
Let’s move on, shall we?
Basal Body Temperature (BBT)
This is your temperature when resting and can help you predict when you are ovulating.
To track your BBT accurately, you will need to take your temperature at the same time every single day, although half an hour earlier or later is also acceptable. Anything more than that will invalidate the results!
You will need to take your temperature the moment that you wake up – before you even get out of bed or even move around too much. Any movements will cause your temperature to increase, and the results will not be accurate.
You also need to have had at least 4-5 hours of sleep before taking your temperature.
Just before ovulation, you will notice your temperature dip ever so slightly. Your BBT will then rise when you are ovulating. You will be at your most fertile a few days before this temperature increase.
To use BBT to track your fertile window, you will need to track your temperature over a few months so that a pattern can emerge.
And finally, on this one – it is best to purchase a special BBT thermometer as these can detect the tiniest of changes in your temperature, which a standard thermometer will not do.
It is worth mentioning that tracking your BBT is not foolproof. Anything can cause a change in your temperature – illness, having an alcoholic drink the night before, stress etc.

Ovulation Predictor Kits (OPKs)
I know this might sound a bit obvious, but it’s imperative to use OPK correctly!
What are OPKs?
OPK’s check for luteinising hormone (LH) in your urine. A rise in this hormone signals your body to release an egg. This will typically occur within 12 to 24 hours. Once the egg has been released, it is only viable for 24 hours, so you need to get down to business ASAP!
When to test
You can test at any time of the day, but it is typically recommended that you limit fluids for 2 hours before testing. Some tests do suggest not using the first wee of the day. You should aim to test at the same time every day.
If you are testing once a day, there is even a chance that you might be missing your LH surge, so you might want to test twice a day.
With OPKs, you are looking for both lines to be the same level of darkness on the test (God knows it’s nice to see two lines on something!) A faint second line does NOT indicate ovulation.
Working out when to use the ovulation tests really depends on your cycle length. Generally, you will ovulate halfway through your cycle, but this isn’t the case for everyone.
For example, if you have a 28 day cycle, you will likely ovulate around CD 14, so you’ll need to start testing around CD 10. If you have a 35 day cycle, you will probably ovulate around day 21-22. If you have a shorter cycle, you will need to start testing earlier.
I had a longer cycle, so I would typically start testing around CD 9 or 10. I purchased the cheaper OPKs from Amazon, so I didn’t mind using them up quickly.
Please be aware that some fertility treatments, such as Clomid, may cause you to get false positive readings on your ovulation tests.
Use An App To Track Your Cycle
Using an app to track your fertile window will definitely make your life easier! I use Ovia and I have found it to be the most user friendly out of all the ones I tried – which was A LOT, believe me!
With the apps, you normally have to input the date of your last period, your cycle length, period length etc. They will then calculate when your fertile window is and your projected period. It is important not to rely on this information too heavily as it is just an app running numbers based on an algorithm at the end of the day.
With Ovia, it’s not just your period information that you enter. It also asks about your mood, symptoms, information on your CM etc. By entering this information, you give the app more information to help it predict your fertile window more accurately. Again, this is not 100% accurate!
Conclusion
Hopefully, with the above information, you will be able to track your fertile window easily. However, as with everything health and fertility-related, nothing is guaranteed. Trying to conceive can sometimes be a very long and challenging road.
So many factors come into play when trying to track your fertile window, such as age, weight, health, PCOS. If you are struggling with trying to conceive, it is always best to get yourself checked out by a medical professional.
Good luck and baby dust to you!
P.S – If you have been a bit confused by all the TTC, BBT and OPK, make sure you check out my trying to conceive acronym post where I explain them all!
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Cover Photo by Debby Hudson on Unsplash
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