Only 13% of women can accurately predict their ovulation and only 55% choose a day of ovulation that is inside their 6-day fertile window.  What does this mean? Almost 50% of the population aren't trying to conceive within their fertile window and almost 90% are missing their most fertile day. Having intercourse during your Fertile Window is essential for optimizing your chances of conception each month. 


What is the Fertile Window? 

The fertile window encompasses about ~6 days of your cycle. It includes about 5 days before ovulation and 1 day after. This is because sperm can survive in the female reproductive tract for up to 5 days under the right conditions (*spoiler alert - the time around ovulation is the right conditions*) but the egg once ovulated is only viable for 24 hours. So this window includes about 5 days leading up to ovulation, the day of ovulation and one day after. Contrary to what we learned in elementary school health class, you can only get pregnant about ~6 days each month.  


How do I Track my Fertile Window? 

Fertility education & awareness is ESSENTIAL for conception. Understanding your cycle, when you're ovulating and which days quality as your fertile window is essential for conception. And this is more than just using your cycle tracking app (which has about a 21% accuracy for predicting your day of ovulation).


I'm going to share my top clinical insights on how to properly use Ovulation Predictor Kits (OPKs), cervical mucus and basal body temperature tracking to accurately predict your ovulation. Why? Using methods like LH or Estrone‐3‐glucuronide (E3G) urine strips or Fertility Awareness Methods (cervical mucus, basal body temperature tracking + cycle tracking apps/calenders) - significantly improves conception and pregnancy rates.


CYCLE TRACKING APPS


Using an app can be a very effective way to track your cycle, basal body temperature and cervical mucous. Not all apps are created equal. Often apps contain misinformation or ads for non-scientific products that can be confusing and not helpful. Remember, using an app in isolation is not effective at predicting your true day of ovulation - in combination with other fertility awareness methods, it becomes a potent tool!


The following few apps have been shown to have the best reliability and focus on the science of your cycle. 

1. Glow ovulation period tracker. This is a subscription app with a monthly fee.  

2. Fertility Friend FF. This is the oldest and possibly most used fertility app. There is a free and paid version (you may want the paid version).  

3. Clue. This is a paid monthly subscription. Clue does an excellent job of tracking the cycle. It has less information about IVF and other fertility support than the other apps.


CERVICAL MUCOUS

Your cervical mucus changes in relation to the hormonal fluctuations that occur throughout your cycle. Your cervical mucus should become creamy leading up to ovulation (this is your semi-fertile window) and should then turn clear and stretchy (we call it "egg white") at ovulation and during your most fertile window. This egg-white cervical mucus has a pH and texture that are protective for sperm (unlike your luteal phase cervical mucus) + it's a sign that you're in the ovulatory window. If you're actively trying to get pregnant - this is your time! 


How to Track Your Cervical Mucus  

Begin tracking cervical fluid the first day after your menstrual period ends,  the best time to assess your cervical mucus is first thing in the morning (while sitting on the toilet).

  • Observe your underwear for any discharge; colour, amount, and whether it dissolves into the fabric.  

  • Before urination wipe front to back and note how easily the tissue glides (ex. dry, smooth, lubricative)

  • Pick up the discharge and feel it between your thumb and middle finger does it feel Dry? Sticky? Creamy? Slippery? Lubricative?  

  • Separate your thumb and middle finger; does the fluid stretch? If so, how much before it breaks?  Note: your most fertile cervical mucus will be very stretchy Note the colour (white, yellow) and quality (creamy, clear) of the discharge

While detecting changes in cervical mucus isn't an exact science it does help us hone in on our fertile window and is an excellent indicator of when we should start to use OPKs or LH strips.


LH / OVULATION PREDICTOR KITS (OPKs)

One of the best ways to PREDICT ovulation. The LH surge occurs about 24 hours before our actual day of ovulation and the day of the surge is arguably the most fertile day of the cycle!


Proper use of LH strips/OPKs is incredibly important to produce accurate & reliable results. Please follow each of these steps: 

1) Start testing before ovulation, approximately 4 days before you expect ovulation to occur. Eg. If your cycle length is 28 days, predicted ovulation is on day 14, start testing on day 10 

2) Don't test with first-morning urine, we need to give the LH time to move through your body/to be processed into your urine. Take the test in the middle of the day, anytime between 10 am-2 pm 

Eg. Noon on your lunch break. If desired, test once more in the evening after dinner (although not necessary). 

3) Urinate in a cup, and dip your LH strip into the cup vs. urinating right on the stick/strip 

4) If using a line-based test, you are checking to see when your line becomes as dark as the control line or darker (indicates a positive surge) 

5) Digital tests often give a peak reading or smiley face (indicates your positive surge) 

6) When you get an LH surge, it means you will ovulate the next day. Plan intercourse for that day and the following day. 

7) But, don't stop here! Keep testing until you get a negative result, we want to see this pattern: (-) (-) (+) (+) (+) (-)   (-) as an example. We want to see negatives on each side of the positives


NOTE: some new options like Premom, combine a stip and digital technology to help you quantify LH and determine the exact day of your LH surge.


Basal Body Temperature (BBT)

Your Basal Body Temperature (BBT) is the best sign to confirm ovulation and pinpoint your ovulation date with a high degree of precision. This is because your BBT responds to the hormone progesterone, which is only present in high amounts after ovulation.


When you consistently record your BBT, you can see that temperatures are relatively lower before ovulation and higher after ovulation. Once a few higher temperatures are observed, ovulation can be identified as the day before your temperature rises.In most cases, you will have lower pre-ovulation temperatures and higher post-ovulation temperatures. Your temperature may rise slowly in increments, or quickly, or it may even rise and fall slightly over several days.


The temperature rise is usually about 0.4 - 0.8 degrees Fahrenheit or 0.2-0.5 degrees Celsius. More important than the value of the rise, is the overall pattern of the chart (lower in the follicular phase and consistently higher in the luteal phase) NOTE: Using the BBT method, ovulation is discovered in hindsight. After 3 months of temperature monitoring, you can predict the day of ovulation and act accordingly!


Ways to Track 

1) BBT Thermometer (has 2 decimal places for increased accuracy)

  • Take your temperature as soon as you wake up in the morning, before doing anything else (including sitting up)

  • Take your temperature at the same time every morning (or as close to the same time as possible)

  • Make sure that you’ve had a solid few hours of sleep (read at least 3), this includes getting up in the night to use the washroom!

  • Enter your data on a chart or directly into an app

2) Biometric wearables (like the Oura Ring)

3) Femtech (like Tempdrop)


Options 2 and 3 are preferable because they collect the data in the background and average it over time. There is less mental burden associated with their use and the multiple data points help reduce confounding factors to body temperature like alcohol use, poor quality sleep, movement through the night etc.

Line graph of temperature by day 1–33 with peak around day 26 and “Ovulation” arrow near day 25.

SAMPLE BBT CHART

Menstruation = temperature remains elevated until about CD3

Follicular = lower BBT 

Ovulation = the last temperature dip

Luteal = elevation in temperature of 0.2-0.5 C or 0.4-0.8 F (this should be sustained until 1-2 days before menses at which point it drops and flow begins)


Optimizing your Fertile Window for Conception

Now that you've identified your Fertile Window, how can you optimize it for conception?

By having timed intercourse, as frequently as possible, during this window. Remember, your fertile window is approximately 5 days before ovulation and 1 day after. Your MOST fertile days are the 2 days leading up to ovulation (including the LH surge) and ovulation itself. Try to have intercourse every day to every other day in your ‘fertile window’, ensuring you’re prioritizing intercourse on the day of your LH surge and the day of ovulation.

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About the Author

Dr. Liza Klassen, ND

A fertility-focused ND who bridges the medical and emotional aspects of fertility, recognizing that the journey to conception is not solely clinical but also deeply personal. She is passionate about helping her patients achieve and maintain healthy pregnancies whether natural or assisted and works collaboratively with reproductive endocrinologists and ART team to deliver high-quality & efficacious care.