When is Your Fertility Window? How to Biohack Your Cycle

This post may contain affiliate links. Read about our privacy policy.

Whether you're trying to get pregnant OR avoid it, it's important to understand how your body works, track your menstrual cycle, and know when you have a peak fertility window and can actually conceive a baby. Our resident guest doctor and fertility expert is sharing what all women need to know about conception and ovulation in this post!

When is your fertility window?
Medically Reviewed Post

This guest post is by Dr. Cleopatra Abdou Kamperveen, The Fertility Strategist and Executive Director of the Fertility & Pregnancy Institute. The mission of the Fertility & Pregnancy Institute is to see what others can’t using the best of love, science, and commitment to help ensure that your fertility keeps up with your high-achieving life so that you get to have as many superbabies as your heart desires.

View Author Profile »

Dr. Cleopatra Abdou Kamperveen is a scientist and university professor who pioneered the field of fertility biohacking and creating superbabies. She specializes in fertility, pregnancy, and how health is transmitted from one generation to the next. To date, she has received nearly $3 million in grant funding from the National Institutes of Health, the National Science Foundation, the Robert Wood Johnson Foundation, and others. Dr. Cleopatra Abdou Kamperveen has been cited more than 1,000 times in the past 5 years alone.

Dr. Cleopatra and Oprah

Dr. Cleopatra Abdou Kamperveen teaches women about the primemester—the magical and powerful window of opportunity before pregnancy—when we literally have the power to change the quality and expression of the genes that we pass down to our babies and grandbabies.

Using the science-based, big-hearted Primemester™ Protocol developed and refined by Dr. Cleopatra Abdou Kamperveen over the past 24 years, the Fertility & Pregnancy Institute helps women all over the world reverse reproductive aging, get pregnant quickly and easily (with a 97% success rate!), reduce miscarriage risk, and finally have the superbaby they have been dreaming of for as long as they can remember. Dr. Cleopatra Abdou Kamperveen is the author of the forthcoming book, “Primemester to Your Superbaby.” Over to you, Dr. Cleopatra Abdou Kamperveen! 

Whether you’re considering forgoing hormonal birth control for more natural methods or you’re starting to plan for a baby, biohacking your cycle will help you get there in shortest amount of time. 

Pregnant woman walking away from a staircase.

Should You Be on The Pill (+ Other Types of Hormonal Birth Control)?

I should start by saying that I absolutely am not hating on The Pill.

(And please note here that I'm going to use ‘The Pill' as shorthand for the birth control pill and all other hormonal birth control, including hormone-releasing IUDs, injections, patches, etc.).

While it is true that religion and other personal characteristics strongly influence attitudes toward The Pill, we can all agree that the pill revolutionized the world for girls and women because it put family planning in their hands in a way that had never been possible before. 

In fact, much of the world that lags in development, social progress, and social justice does so because its girls and women do not have access to The Pill and, therefore, don't have the ability to control their family planning to the same degree. So, without question, I celebrate The Pill for how it has allowed girls and women to access to their full power and self-authority. 

That being said, The Pill and other hormonal birth control are not without short- and long-term consequences. These can include a wide range of health consequences, from increased risk of depression to increased risk of insulin resistance—both of which may actually affect fertility. 

RELATED:  7 Reasons to Go Off The Pill: The Truth About Birth Control Pill Side Effects

It is important for us to be educated about the possible health consequences of The Pill, but what I most want to draw your attention to today is a universal (and commonly-overlooked) side effect of The Pill: that it masks what our unique female bodies would be doing naturally. This means that we are missing out on critical information about our cycles, our fertility, and our health more broadly. 

Your period is a vital sign, just like your heart rate, blood pressure, and temperature. A vital sign is an observable, measurable quality that makes visible the body's ability to perform fundamental and essential body functions. And, reproduction definitely falls into the category of a fundamental body function.

If, as a society, we truly treated the period as a vital sign, we would begin monitoring our cycles as soon as we started getting our period, and certainly long before we plan to get pregnant, just like we do with body temperature, blood pressure, and other vital signs. 

A woman sitting down in a grey dress holding her pregnant belly.

When is Your Fertility Window?

There is only one day each cycle when you can get pregnant!

Most people are shocked to learn that there's actually only one day—or even less than one full day—each month in which an egg can be fertilized. This is critical to know whether you want to get pregnant or are learning how to prevent pregnancy naturally.

Now that I have shocked you, let me provide a few definitions before we go any farther.

A menstrual cycle is not just the period of time that you are bleeding; it is the full cycle. Day 1 of your cycle is the day you start bleeding, and the last day of your cycle is the day before your period starts again.

A normal or healthy menstrual cycle is clinically defined as a cycle lasting anywhere between 21 and 35 days, although cycles on the shorter end of normal may be more likely to have an insufficient luteal phase (or latter phase of the cycle). A recent study of 98,903 women showed that 95% of women have cycles between 20 and 40 days long, so it may be that we should be adjusting our clinical definition of a normative cycle as time passes.

RELATED:  The 5 Most Common Women's Fertility Misconceptions

Also, just a note that I'm going to say “each month” for simplicity, but the most accurate thing to say is “each cycle” because, as noted above, the menstrual cycle is not necessarily a month long. 

Back to the shocking fact that you only have one day per month (or cycle) when your egg can be fertilized. This is because once an egg is released—what we know as ovulation—it only lives for 12 to 24 hours. And it’s only during this 12- to 24-hour period that an egg can be fertilized. After all, it's only during the period that the egg is actually present that it can be fertilized. 

Woman in her first trimester holding a sonogram photo

There is only one day per month when you can conceive, but you are fertile for six days each month.

It is not the case, however, that you're only fertile for 12- to 24-hours each month. You're probably wondering how that's possible. Let me explain. 

The number of fertile days you have each month is the product of the overlap in the lifespan of sperm and the lifespan of an egg (or eggs in the case of multiple eggs being released during ovulation—what could become fraternal twins).

So, in essence, what a fertile day in the life of a female means is this: If a sperm entered the reproductive tract on that particular day, it could survive long enough to reach an egg that will be released during ovulation and will go on to live and, thus, be available for fertilizing for just that 12- to 24-hour period after it's released.

Hardy sperm can live for up to five days within the female reproductive tract, which means—bearing in mind the definition of a fertile day that we just covered—that you have up to six fertile days each month. Specifically, these are the exact day you ovulate and the five days before ovulation. 

A pregnant woman and man holding hands outside looking towards each other.

When are your peak fertile days for conception?

You have two to three peak fertility days each month.

A study published in the New England Journal of Medicine in the 1990s demonstrated that the likelihood of conceiving was nearly identical on the day of ovulation and the day prior to ovulation (approximately 30%). As a result of this study, these two days of the month have become widely accepted as peak fertility days, meaning that you are far more likely to conceive as a result of having sex on these two days than on any other day of the month.

RELATED:  Fertility Treatment: Overview of Mind-Body Tools + Resources

Interestingly, very recently, a large study of 225,000 cycles from nearly 99,000 women observed a very different pattern which emphasizes concentrating on the day before ovulation for getting pregnant.

In this study, even the two and three days prior to ovulation were more fruitful in terms of pregnancy achievement than the day of ovulation. The likelihood of getting pregnant was 27% three days before ovulation, 33% two days before ovulation, and a whopping 42% the day before ovulation. On the day of ovulation, likelihood of getting pregnant dipped to 20%.

A pregnant woman in a denim shirt with her hands around her belly.

The point here is that if we can identify the day of ovulation with near-perfect precision, then we have great chances of getting pregnant, as well as the ability to avoid getting pregnant. But notice that, whether for the goal of pregnancy achievement or the goal of avoiding pregnancy, what is crucial to know is that we are going to ovulate before ovulation actually happens

If the goal is to get pregnant, focus on the three days before ovulation, and, especially, the day before ovulation. If the goal is to avoid pregnancy, a barrier method should be used for the 9-day period, starting seven days before ovulation and ending one day post-ovulation. (You will notice that this 9-day period is longer than your six fertile days; this is because the recent study found that some small percentage of pregnancies occurred beyond the six-day fertile window.)

In my next Root+Revel article later this year, I will teach you how to use your cervical fluid to get even more clear on your most fertile days of the month.

RELATED:  Women's Health Tracking Tools to Track Periods, Increase Fertility + Balance Hormones

An important note is that period-tracking apps should not be relied upon as the sole source of information for identifying ovulation, since you will not ovulate on the same day each month and most apps cannot adequately account for monthly variability in day of ovulation.

For the greatest precision humanly possible without ultrasound, use a system like our Get Pregnant in No Time Formula (the modern woman’s version of Taking Charge of Your Fertility) taught as part of the Primemester Protocol, and rely on your app only as an electronic calendar of your cycle.

Traditional Medicinals teas and products for moms.

How Do I Know If I'm Ovulating?

After predicting ovulation with near-perfect precision to achieve or avoid pregnancy, the next step in biohacking your cycle is confirming that ovulation occurred and that your body experienced the expected hormonal shifts post-ovulation.

If your goal is to get pregnant, it is critical that you experience a spike in both estradiol and progesterone with ovulation (and this is important for your health even if you aren’t trying to get pregnant). The spike in these two sex hormones will peak approximately seven days post-ovulation. When this spike occurs and is sustained for long enough, it ensures that you have the ability to both get, and stay, pregnant. 

In the past, there were just two ways to confirm whether you ovulated (without ultrasound):

  1. You could chart your temperature. With this method, you are looking for a tiny post-ovulation temperature spike that is easy to miss (and, critically, that cannot be used to predict ovulation in order to avoid or achieve pregnancy).
  2. Alternatively, you could go into your doctor’s office to have your progesterone tested via blood draw. These days there is an even easier option: at-home urine testing of Pregnanediol Glucuronide (PdG). In the Get Pregnant in No Time Formula, we recommend the Proov PdG test strips for this purpose. Proov at-home testing allows you to confirm ovulation and to evaluate the health of your luteal phase by confirming that your progesterone has remained elevated long enough post-ovulation.

This has been your primer on biohacking your cycle. As women, it is our right to know this information and is a beautiful privilege to invest the time and love in knowing our bodies this intimately, both for our future families and for our health and longevity.

Sending you love and all the baby dust (for whenever you want it), Mama!

Dr. Cleopatra Abdou Kamperveen

Been trying for a baby with no luck, or planning to start trying soon? 

This checklist will get you on your way!

Get immediate access to the Ultimate 2-Minute Checklist of Scientifically Documented Strategies for Getting Pregnant, Reducing Miscarriage Risk, & Finally Having Your Superbaby.

Thanks again to Dr. Cleopatra Abdou Kamperveen for sharing her wisdom with us!

Visit Dr. Cleopatra Abdou Kamperveen here to schedule a complimentary fertility consultation with the Fertility & Pregnancy Institute, and follow her on Instagram or join her free community on Facebook here

Visit The Fertility & Pregnancy Institute here to learn more about the Primemester Protocol and Fertility Epigenetic Tailoring.


Faust, L., et al. (2019). Findings from a mobile application-based cohort are consistent with established knowledge of the menstrual cycle, fertile window, and conception. Fertility & Sterility, 112(3), 450-457.

Godsland, I. F., et al. (1992). Insulin resistance, secretion, and metabolism in users of oral contraceptives. The Journal of Clinical Endocrinology & Metabolism, 74(1), 64–70. 

Skovlund, C. W., Mørch, L. S., Kessing, L. V., & Lidegaard, Ø. (2016). Association of hormonal contraception with depression. JAMA Psychiatry, 73(11), 1154-1162.

Wilcox, A. J., Weinberg, C. R., & Baird, D. D. (1995). Timing of sexual intercourse in relation to ovulation—effects on the probability of conception, survival of the pregnancy, and sex of the baby. New England Journal of Medicine, 333, 1517-1521.

About The Author

2 thoughts on “When is Your Fertility Window? How to Biohack Your Cycle”

  1. The day of ovulation is the benchmark defining the six potentially fertile days of the menstrual cycle—that is, the five days before ovulation and ovulation itself. This fertile window was estimated from the present study, confirmed in a reanalysis of British data, and reported as a preliminary finding from a multicentre European study. Thank you for being thoughtful about sharing these very valuable and helpful pieces of information!

Leave a Comment

Your email address will not be published. Required fields are marked *