While some old wives’ tales and even movies or TV shows would have us believe that a child can be conceived at any time after having unprotected sex, there are actually just about a week’s worth of days in each month where a woman can become pregnant. This means that if you’re hoping to become a mother-to-be, you’ll benefit from tracking the days on which you’re most likely to conceive. Understanding how to track these monthly fertility cycles can ultimately help you start your family sooner, and can be particularly helpful if you’re having trouble getting pregnant. One way to track your ovulation is through the calendar method.
Understanding Fertility: The “Fertile Window”
There are a lot of misconceptions out there about when a woman is “fertile,” or able to get pregnant. For example, a poor but common theory is that every woman should try to conceive a child on day 14 of her menstrual cycle - or, 14 days after the beginning of her last period. The truth is, you can only successfully conceive a child during your “fertile window.” The dates of this window will vary from woman to woman, depending on the length and dates of her menstrual cycle.
Because of this, day 14 in a woman’s cycle may not necessarily be the best day for her to conceive.
So when is the best day to try and conceive?
This will depend on the dates of your own “fertile window.” A woman’s fertile window can last anywhere from five to eight days, and will usually begin up to five days before ovulation takes place. This is because the egg that’s released when you ovulate has a brief lifespan of 24 - 48 hours; however, sperm from a male partner or donor has a lifespan of up to five days after ejaculation. The “fertile window” timeframe therefore reflects the lifespan of both egg and sperm.
Since pregnancy is only possible when a viable egg is present and able to be fertilized, a fertile window usually includes the five days before ovulation and the day of ovulation. If you engage in intercourse five days before ovulation, most doctors would say you have about a 10% chance of a successful natural conception. However, the probability of you becoming pregnant rises steadily each day afterward, up through your ovulation date. In fact, fertility research has shown that the three days leading up to and including ovulation are likely your most fertile days.
What if you don't know when your fertile days are?
If you are not aware of your own “fertile window” dates or when you ovulate each month, experts recommend engaging in sexual intercourse every 2 to 3 days to help optimize your chances of conceiving. However, there are also several ways you can try to narrow down and track your most likely date of ovulation from month to month. One such method is the calendar method.
What is the Calendar Method?
The calendar method, sometimes referred to as the rhythm method, is one of several fertility awareness methods that can be used to determine the days of the month you are most likely to get pregnant. These methods are referred to as natural family planning methods, since they each track the body’s natural functions and indicators to determine a date for optimal fertility. (This method can be used by couples that want to conceive and who want to avoid becoming pregnant. We’ll be focusing on how it can be used to help conceive.)
The calendar method requires that you track your menstrual history. This can help you determine when you’re most likely to conceive by highlighting timing and patterns in your menstrual cycle, including when you’re most likely to ovulate.
Two versions of the Calendar Method
If you use the calendar method, you’ll first need to decide which version of the calendar method to use. If you want to try to use the method to begin conceiving sooner, rather than later, you can use the shorthand method. You’ll have to:
- Figure out the likely start date of your next period.
- From that day, count back 12 days. Then, count back another four. This five-day range will be an approximation of your fertility window for the upcoming month.
However, the shorthand method of the calendar method does not account for any long-term patterns or fluctuations in your monthly cycle. Because of this, while you can use the shorthand method to increase your more immediate chances of conception, you should also begin using the longhand calendar method. In doing so, you’ll track your cycle for a few months. This will give back a wider range of possible fertility dates that accounts for the cycle variations that most women experience from month to month.
To use the long-hand calendar method, you should:
- Plan on tracking your menstrual cycle for 8 to 12 months. During the tracking process, count the number of days in your monthly cycle - the day you start your period is the day your menstrual cycle begins.
- After tracking over a period of time, find the longest and shortest of the cycles that you tracked.
- You’ll need to carry out some basic math to help determine the date zone in which your fertile window.
AmericanPregnancy.org has written out exactly how to solve this problem:
- To find the first possible day of your fertile window, subtract 18 days from the length of your shortest cycle. (Ex. “If 26 days was your shortest menstrual cycle, take 26 and subtract 18 to come up with the number 8. This means that the first day of your fertility window starts on the 8th day of your cycle.”)
- To find the last possible day of your fertile window, subtract 11 from the length of her longest cycle. (Ex. “If 32 days was your longest menstrual cycle, take 32 and subtract 11 to reach the number 21.
- Once this math has been completed, you’ll have the earliest and latest possible days in your monthly fertile window. The days in between will be the days you’re most likely to conceive. (In AmericanPregnancy.org’s example, the fertile window would most likely fall between 8th day of your cycle to the 21st day of your cycle.)
Pros And Cons Of The Calendar Method
While the calendar method is one of the most basic tracking methods available for couples interested in increasing their chances of a successful natural conception, there are both pros and cons to consider when using this method:
Pros of the Calendar Method
- This method is entirely free to use. All you need when using the calendar method is a calendar and a pen - or even an app or online tool if you choose to use one for tracking and recording your information.
- This method is risk-free, as it requires no use of invasive tools, medications, or any outside sources that could negatively affect your body or that would be considered risky to use.
Cons of the Calendar Method
- The calendar method requires time to discern a real pattern in your cycle. Unless you have a history of tracking your cycle dates, you’ll likely need to plan on tracking your menstrual cycle for 8 to 12 months before you can use this method successfully.
- This method may not be a good fit for every woman; in fact, it’s best used by women who have extremely regular menstrual cycles and ovulate regularly at the same time each month. This, unfortunately, means that it will be less accurate when used by women with irregular or inconsistent cycles, as they are unlikely to ovulate on a discernable schedule each month.
- In addition to being a bad method for women with irregular cycles, the calendar method will often not yield accurate results for women whose cycles are shorter than 26 days or longer than 32 days.
- Outside factors like stress, illness, and disruption of normal routine, may throw off a woman’s ovulation cycle, and cannot always be accurately accounted for by this method.
While there are a number of limitations to consider when using this method, you don’t necessarily need to write it off as too unreliable to use. Many experts believe the calendar method is a valid tracking option. However, it is best used in combination with other tracking tools and methods. Experts particularly recommend using an ovulation or fertility monitor to maximize the chances of successfully tracking your cycle and to confirm when ovulation is occurring.
Our Thoughts On The Calendar Method
The calendar method is just one possible way you can track your ovulation cycle. When used in combination with another method, it could quickly become a valuable resource in piecing together a complete picture of your fertility cycle.