So let’s go back to basics with our friends at Daysy – who created a device to help you find your fertile window more easily. The fertile window happens around the ovulatory phase of your menstrual cycle. When you ovulate, an egg (or two – hello twins!) is released from the ovary and moves through the fallopian tube, at which time it can be fertilized if live sperm have made it up there. While the lifespan of an egg can be up to 24 hours, sperm can live inside an ovulater no longer than 5 days* (1). The fertile window is the time in which both the egg and sperm are viable, which is in total around 6 days (2) and conception is most achievable 2 days before ovulation. But, beware. Those 6 days can move around in your cycle as you may not always ovulate on the same day. This is where cycle tracking and our friend Daysy comes to help us out.
How to find your fertile window
The traditional method of finding your fertile window is using your cervical fluid and basal body temperature. While your cervical fluid can cue you in to how fertile you are, can help show you that are likely going to ovulate soon, your basal body temp tells you when you’ve ovulated (after the fact).
You can use the color and texture of your cervical fluid (yes, that’s that stuff in your underwear!), to help assess where you are in your cycle. Who knew discharge could be so useful, right? At the least fertile phase of your cycle, right after your period, you might have some days with not very much discharge (3), or your fluids may feel dry or sticky. As your cycle goes on, your fluid may become whitish or yellowish, with a more creamy consistency. You’ll likely feel more moist. At peak fertility, cervical fluid is typically stretchy and clear like egg whites. Post ovulation, cervical fluid becomes dry or sticky once again.
Why does the fluid change so much? To either support the sperm on its journey! The molecular structure of your cervical fluid can either make it easier, or harder for sperm to swim and survive. Your body is smart that way! Why allow the sperm all the way up there, invading your space, if there’s no egg anyway?
Tip: While assessing your fluids can be a useful tool, do know that outside factors can affect its texture and color – like various medications, vaginal infections and dehydration. This is why using it in conjunction with other measurements is key.
BODY BASAL TEMPERATURE
Your BBT is your temperature when you’re at rest. For this reason, to get your BBT you need to take your temperature as soon as you wake up. No getting up to pee first! The reason that tracking your temperature can help find your fertile window is that during ovulation, your temperature increases by 0.25-0.45 degrees celsius (4) or 0.45 – 0.81 degrees fahrenheit. So, by tracking your temps throughout your cycle, you can see when that shift has occurred, and know that you have likely ovulated!
You may be thinking to yourself, hmmm that’s such a small increase! What if I miss it? How do I know if my thermometer will be able to pick up such a tiny shift? This is what we love Daysy for. Based on 10 million cycles, Daysy is a highly calibrated sensor plus unique algorithm that automatically calculates your BBT and tells you, using different colored lights, whether you’re in your fertile window or not. Red is for your fertile window, green for your non-fertile days, and yellow for when you’re cycle is shifting All you gotta do is put their thermometer under your tongue first thing in the AM, and let it know if you are on your period, and BOOM! And, if you wanted to, you can track your cervical fluids in the app too! (Although this information won’t get integrated into the algorithm or fertility calculations). How much easier can learning about your body get?
*Please note, Daysy is not a form of birth control, but rather a tool to help you know when you’re fertile.
SOME WORDS TO THE WISE
- While it is more rare, during your fertile window, even pre-cum can be viable. More on getting pregnant via pre-cum here.
- If you are on hormonal birth control or an IUD, your fluid and temperatures may not accurately represent where you are in your cycle (depending upon your birth control, you may not actually be cycling) and you can’t use Daysy if you’re on any form of hormonal birth control
- If pregnant, knowing your unique cycle-length will be helpful in ensuring your Estimated Due Date is at least somewhat on track. This can come in handy when it comes to Induction talks for hospital-based births.
- Many apps and even doctors use Day 14 as the stand-in for Ovulation Day. But most people actually don’t ovulate on that day. So, unless you’ve tracked your cycle and saw that you actually do ovulate on Day 14, don’t use it as a stand-in. And remember, while you may have ovulated day 14 one cycle, this doesn’t mean you will the next cycle!
WHY WE THINK IT'S COOL
Becoming aware of your unique fertile window gives you amazing insight to your body. A lot of sex education (if you were lucky to get any at all) is about preventative measures: how not to get pregnant, how not to get STIs, and so on- that body literacy can take a backseat. By learning to find your fertile window, you can start tuning in to how your body and mind are connected to your menstruation. Do you feel differently during that time of the month? Do you crave different foods? Want to participate in different activities? Plus, If you don’t want to get pregnant, you can make sure you’re staying well protected during that time. Or, if you want to conceive, you can use that window wisely!
What’s more, learning the indicators of the Fertile Window can clue you into a whole lot more about your body’s overall state of health. Maybe you notice your cervical fluid isn’t changing. Or your temperatures aren’t rising. This is important info to bring to your health team to help assess if your hormones may need a little support.
See, it is pretty cool, eh?
*Editor’s note: While most research says that sperm can live up to 5 days in the reproductive tract, we did find some research that says 7 (5, 6). However, the odds are low. In one study, there was just a 5% probability of sperm living more than 4.4 days and just a 1% probability of it living more than 6.8 days (6). Using a fertility tracker like Daysy? Don’t worry! Most account for 9 fertile days minimum, just in case.
Written by: Martha Michaud
All content found on this Website, including: text, images, audio, or other formats, was created for informational purposes only. The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
(1) Pagano, Trina. “Sperm: How Long Sperm Live, Sperm Count, and More.” WebMD. WebMD, October 30, 2018. https://www.webmd.com/infertility-and-reproduction/guide/sperm-and-semen-faq#1.
(2) Wilcox, A J, C R Weinberg, and D D Baird. “Timing of Sexual Intercourse in Relation to Ovulation. Effects on the Probability of Conception, Survival of the Pregnancy, and Sex of the Baby.” The New England journal of medicine. U.S. National Library of Medicine, December 7, 1995. https://www.ncbi.nlm.nih.gov/pubmed/7477165/.
(3) Parenthood, Planned. “What Is the Cervical Mucus Method?: Cycle, Stages & Chart.” Planned Parenthood. Accessed November 21, 2019. https://www.plannedparenthood.org/learn/birth-control/fertility-awareness/whats-cervical-mucus-method-fams.
(4) Valley Electronics. “Technology.” Technology – This is how Daysy works. Natural ovulation tracking. Accessed November 21, 2019. https://usa.daysy.me/technology/.
(5) Ferreira-Poblete, A. “The Probability of Conception on Different Days of the Cycle with Respect to Ovulation: an Overview.” SpringerLink. Kluwer Academic Publishers. Accessed November 21, 2019. https://link.springer.com/article/10.1023/A:1006527232605.