Here's the question I asked:
"About how many days are you fertile in each cycle?"
First of all, it's worth noting that the question I asked was not very specific, and I think that may have caused some confusion and also explains the wide range in answers. Some women answered with the fertile window of the egg itself (24-48 hours max), while others replied with the range of dates that pregnancy would be likely due to an open cervix and abundance of cervical fluid (up to 10 days or possibly longer).
Do you want to know the real answer?
- During a normal 28-day cycle, the average amount of days a woman is considered fertile (where sex is likely to lead to conception) is usually 8-10 days, or roughly one-third of your cycle. ("Average" is the key operative word here.)
- The amount of days that YOU are fertile per cycle can (and does) change cycle to cycle. It depends on your current cycle, your cervical fluid, and cervical position. In other words, every single cycle could have a different amount of fertile vs. non-fertile days.
The majority of this post will focus on Answer #2. While it's helpful to know generals of fertility, if you are using fertility awareness for conception (and especially if you are using it as contraception), it's vital that you know when your fertile vs. non-fertile days are.
Since defining fertile days can take a slightly different approach depending on how you're using fertility awareness (either as contraception or help getting pregnant), we'll address it from both angles.
I'M TRYING TO GET PREGNANT. WHEN AM I FERTILE?
When you're trying to get pregnant, you are most likely to be successful in the days leading up to ovulation. Your most fertile days are the days with cervical fluid present, when your cervix is soft, high, and open.
Let's take a look at two sample charts and calculate some fertile days. Both charts are from the same woman over two different cycles.
- If you haven't had a cycle shorter than 25 days out of the last 12, usually the first 3-5 days of your cycle are considered infertile days (as are any dry days). So on this chart, there would be virtually zero chance at conception until at least CD8.
- On CD8, creamy cervical fluid has started. While it is possible to get pregnant when having sex on a "creamy" day, it's still fairly unlikely. Notice also that the cervix is not fully open. I would say CD8-9 are potentially fertile, but still unlikely, fertile days.
- From CD10, we start to see a fully soft, high, open cervix and egg white cervical fluid. This is your waving flag to start the race! These days are considered very fertile. You'll see the egg white lasts solidly through CD16, with ovulation happening on CD14 or 15.
- Because the egg is usually released the day before or day of your temperature shift and only lives 24-48 hours, having sex in the days after ovulation is statistically less likely to lead to pregnancy. It's not impossible, but a lot less likely. If you're trying to get pregnant and you want to cover ALL the bases, it's a good idea to continue to have sex until three DPO (days past ovulation). After the third day of a confirmed ovulation and temperature shift, you are infertile again.
So, in this cycle, we had around 8 days of fertility, starting on CD10 with egg white cervical fluid, and ending on the third day of the temperature shift.
Let's take a look at the second chart.
- As with the previous chart, the first 3-5 five days + dry days are considered infertile. So on this chart, the fertile window doesn't begin until CD 12. (You'll notice I skipped over CD9, which was a sticky day. Again, it's technically possible to get pregnant with sticky cervical fluid, but chances are unlikely. If you're TTC (trying to conceive), there's no harm in having sex on this day, but it's unlikely to lead to pregnancy in this particular instance. If you're TTA, though, you would count that as a "fertile" day just to be safe. More on that in the next section.)
- CD12-CD18 would be the maximum fertile window. Even though there are a few days where there is no egg white cervical fluid, the cervix is high, soft, and open, and sperm can live up to 5 days in egg white cervical fluid. Again, when you're TTC and want to cover all the bases, it's a good idea to have sex every day leading up to ovulation, after your fertile window has opened.
- After the third day of the temperature shift (CD18), regardless of your cervical fluid, the egg is either long gone or fertilized, and your chances at conceiving are back down to zero.
This cycle had a 7 day fertile window total. How is it possible to get pregnant several days before ovulation if the egg only lives 24-48 hours? Two key things: the amazingness of fertile cervical fluid and the awesomeness of sperm. With those two factors combined, sperm can hang out in your fallopian tubes for up to 5 days, waiting for the egg to be released and promptly fertilized.
To summarize: when trying to get pregnant, the days leading up to ovulation are key. In particular, any day preceding ovulation where you have egg white cervical fluid and a soft, high, open cervix is a "GREEN LIGHT GO!!!!" kind of day.
Next: what do fertile days look like when you're TTA?
I'M TRYING TO AVOID PREGNANCY. WHEN AM I FERTILE?
DISCLAIMER: THIS POST IS NOT SUFFICIENT TO PRACTICE FERTILITY AWARENESS AS BIRTH CONTROL. PLEASE FIND A FERTILITY AWARENESS EDUCATOR TO HELP YOU ONE-ON-ONE.
As we did with the TTC (trying to conceive) section above, let's define a "fertile day": any fertile day is a day where you have a clear chance of getting pregnant. A non-fertile day is a day where it is either physically impossible to get pregnant or statistically so unlikely that it is an insignificant risk.
When calculating fertile days while trying to avoid pregnancy, it is in your best interest to be as conservative as possible. If you're not sure if you're fertile or not that day, it's best to abstain or use a backup form of protection until you can see a clearer pattern emerge.
Let's look at those charts again, through the lens of trying to avoid pregnancy.
- Under the First Five Days rule, provided you had a clear temp shift/ovulation the previous cycle and your last 12 cycles have been at least 25 days or longer, the first five days of your cycle are safe for unprotected sex (see more on the First Five Days rule here. After your period ends, any day with no sticky/creamy/egg white cervical fluid is a dry day. You are infertile on the evening of any dry day. So, CD 6-8 would also be considered infertile days and safe for unprotected sex.
- On CD9, creamy cervical fluid was reported. Although the chances of conception would be low, under the TTA rules, this would be considered a fertile day. The most conservative interpretation of this chart would probably also count the two days following as fertile days as well, just in case. The presence of ANY cervical fluid, from creamy to sticky to egg white, is considered potentially fertile. Egg white cervical fluid is the most fertile of them all. From CD12 to CD16, you would abstain from sex or use a backup form of protection.
- After ovulation and a confirmed temperature shift, you are safe to resume unprotected sex by one of two rules, whichever is greater (i.e., longer period of time): either the Peak + 4 Rule, or the Temp + 3 Rule. Peak + 4 Rule in this case would be CD21, whereas Temp + 3 would be CD19. The most conservative option would be CD21, so you could resume unprotected sex on that day or after (until the start of your next cycle).
That leaves us with a whopping total of 12 days of possibly fertile days--a much bigger number than the 7-day fertile window on the same chart when TTC.
Why the discrepancy?
Well, it's mostly due to giving yourself a better buffer on either side of your fertile window when TTA. Obviously, if you want to make sure you don't conceive during any given cycle, you'll be more cautious on fertile days in general, and a little more liberal with what counts as a fertile day.
Alright, Chart #2:
- First Five Days Rule + Dry Day Rule means you are safe for unprotected sex until CD7.
- The start of any cervical fluid means CD 8-15 are completely off-limits for unprotected sex.
- After a confirmed ovulation and temp shift, use the most conservative interpretation of Peak + 4 or Temp + 3. This means that unprotected sex would be safe starting on CD20 until the beginning of the next cycle.
WHY IT MATTERS
Anything else to add? Leave me a comment below! :)