The complete guide to finding your fertile window
An analogy
Let’s get our heads around the importance of timing with an analogy.
If sperm were commuters, the egg would be a bus, and the fallopian tube would be the bus stop. The sperm-commuters can arrive up to 4 or 5 days early for the egg-bus. They can happily hang out and wait this long. Much later, and they begin to drop off. When the egg arrives, it’ll wait for about 24 hours. Sperm arriving during this time can also get on the bus. But if the sperm-commuters arrive a day late, the egg-bus will be gone and the next one will not arrive for another 28-ish days.
Having sex during the 2 to 3 days before ovulation gives a couple a 1 in 5 chance of conceiving. This is the most fertile time of the month.
Identifying your fertility window is about making sure the passengers are already waiting at the bus stop.
The Tool Box
There is so single way to best identify your fertility window, and for most women it doesn’t fall at exactly the same point in each cycle. To most reliably predict your window, a combination of a few techniques gives the most reliable information.
Recording your period
Measuring your BBT
Cervical fluid
Ovulation predictor test
Cervix position
Personal signs and symptoms
Record your period
Get yourself a tracker. Either an app or pen and paper. It should look something like this:
Start by recording the dates you have a period. The first day of bleeding is CD1 (cycle day 1). If you get your bleed overnight, the morning you wake up with a bleed is CD1. Using cycle length alone to predict ovulation will give you about 21% chance of accurately predicting ovulation. We need to do better.
Basal body temperature tracking.
A BBT chart tracks very slight changes in your temperature to help you identify when you’re most likely to be fertile.
Here’s how it works; estrogen and progesterone fluctuate throughout the menstrual cycle. Estrogen is the dominant hormone in the first half of the cycle, it is comparatively yin and cooler. When estrogen is dominant, your temperature will be around 36.11 to 36.38.
After ovulation occurs, progesterone is released by the corpus luteam causing a rapid rise in progesterone, a more yang and warming hormone. When progesterone is more dominant, your temperature will rise slightly to around 36.44 to 37 degrees.
This temperature change is very small, a rise is likely to be just .20 to .60 degrees Celsius, but three or more consistently high readings indicates ovulation has occurred.
Charting your temperature daily on a graph, or app with a graph function is the easiest way to interpret your data. If ovulation has occurred, there will be a distinct shift in temperature, this is known as a biphasic chart. You will be able to confirm and retroactively identify the day of ovulation based on your temperature shift. This information becomes useful in identifying patterns, which can help to predict ovulation in the future.
How to do it:
You will need to purchase a BBT thermometer. This differs from a regular thermometer in that it is very specific – temperature needs to be recorded to two decimal places. Every morning, immediately on waking while your body is still technically ‘at rest’ take your temperature in the exact same way and record it on your graph or app. Mark it down on your chart and connect the dots to make a graph.
· Make a note if the temperature could be inaccurate. Things that will influence reliability include
Getting fewer than 3 quality hours of sleep
Having a fever
Jetlag
Using an electric blanket
Drinking alcohol the night before
Stress
Cervical fluid
This is a big one! Monitoring cervical fluid alone can increase your chance of falling pregnant within a certain time frame, independent of intercourse frequency or the use of OTK’s.
The easiest way to check is to wipe the opening of your vagina in the morning before you pee and check the paper, feeling the fluid between your thumb and forefinger. It’s likely to go from:
o dry right after your period
o to sticky
o to thin and elastic and able to be stretched out like an egg white
o to thin and watery
o back to thick or sticky
o back to dry
In a normal cycle, period or “dry days” are non, or less-fertile days and the “thick and sticky” days can be considered to be in the maybe zone.
The fertile fluid we are looking for is that “thin and elastic, egg white consistency”. This fluid is made further up in the vagina and tells us the start of the fertile window is open. Cervical fluid that has lost its stretch and has become slippery indicates that ovulation is imminent.
This very slippery, non-stretch fluid facilitate sperm movement and helps activate the sperm as they pass through the cervix and enter the uterus. I’ve written more about this here.
Ovulation Predictor Kit
OPK is also known as an LH surge test. It’s role is to predict, not confirm ovulation by measuring the surge of the hormone called Lutenising Hormone which precedes ovulation by around 24 hours. Most kits come with 5 or 7 test sticks. It may take a few cycles to sort out, but the aim is to start testing your urine daily a few days before you think you ovulate. (somewhere between day 8 and 11).
The time of LH surge onset to ovulation averages close to 24 hours. Once the LH surge has been detected (ie, a positive), ovulation is likely within 24 hours, indicating that you are likely in the fertile window. Take a note in your Fertility Tracker which day or days you had a positive LH test.
Watch out for the pitfall: The surge can precede ovulation by anywhere between 18 and 36 hours, meaning for some women, relying solely on a positive OTK puts them squarely OUT of their fertile window every month.
Cervix position
Our bodies are amazing! Throughout our cycle, our cervix changes to facilitate fertility. Getting up close and personal with your vagina can give you important information about your cycle. I have written about this in more detail here.
Other signs and symptoms
Record record record. Building a picture of what your cycle is like and how your body responds at different times helps you understand how you feel at each point and helps you see patterns, adding to the accuracy of predicting your fertility window.
Consider:
breast changes
libido
pains
mood changes
cravings
Finally, a note on scheduled sex.
No one particularly likes having sex on a schedule. However, if you are trying to conceive, identifying and taking advantage or your window is really likely to expedite the “trying” part. Of course it would be wonderful if all pregnancies occurred though beautiful lovely spontaneous sex, but sometimes we have to be a little practical and that’s OK.
Still tempted to rely on your app? Take a look here for why it’s not the silver bullet you might have been led to believe.