How Effective is the Calendar Method?

Spoiler: The calendar method only sometimes works

The calendar method, also known as the rhythm method or fertility awareness, involves planning your sex life around your menstrual cycle. Avoid sex during ovulation--that sounds easy enough, right? Well, not really, according to statistics... 

If you're considering the calendar method, here's what you have to know. 

How effective is the calendar method?

To be fair, the calendar method is almost as effective as the pill--but only with perfect use! During its safest, the calendar method is 98.2% effective. But, with typical use, it's between 76-88% effective. That means between 12 to 24 women out of 100 using the calendar method will get pregnant on average. 

What does "perfect use" mean?

Perfect use not only entails strict dates for your frame of ovulation, but also a strictly regular period. For example, even if your period is relatively regular but fluctuates between a couple days early or late, it's more difficult to predict exactly when ovulation begins and ends. If you have unprotected sex during that supposedly "safe" date, you may have a problem. 

How do I implement the calendar method?

There are actually four ways to implement the "calendar method." Also, not all of them require calendars:

  1. The temperature method involves taking your basal temperature using an actual basal thermometer first thing in the morning. When you're ovulating, your body temperature rises slightly to about 97-99 degrees. Without the exactness of a basal thermometer, your temperature could be misread. If you don't do it first thing in the morning, your body could cool down before your resting body temperature has been accurately recorded.
  2. With the cervical mucus method, you need to examine your discharge (aka the ooze in your panties or cervical mucus). When you're ovulating, your discharge is supposed to look and feel similar to egg whites. You need to keep track every day of the look and consistency of your discharge, which is a little more subjective than the exact numbers you would record with the temperature or actual calendar method.
  3. The actual calendar method means tracking your period using a real calendar. Record when your period starts even if you're just spotting (because that counts!) and note when it ends.The standard days method is a variation of this method that involves tracking your menstrual cycle for several months to determine whether or not the range falls between 26-30 days, and then attempting to predict your ovulation days based on some math.

The best way to use the calendar method, also known as the symptothermal method, is to use the temperature, cervical mucus, and calendar methods combined. All three together rank closer to "perfect" use. 

No matter how you're tracking your period, Planned Parenthood recommends tracking your menstrual cycle for at least six periods before using the calendar method in order to be as familiar with your own cycle as possible. That would be six months with either no sex or using non-hormonal methods of birth control. Keep in mind that hormonal methods would mess with your cycle before you even finish observing it.Which, by the way...   

Have you ever thought about how much sex you could actually have if you exclusively use the calendar method?

With about one week of ovulation and another week of menstruation, that leaves about two weeks in a month in which you could have sex. So you would have to decide: do you have time for that? Well, some people combine methods. For example, some women use condoms during ovulation week. 

But if you were looking for a reliable, easy birth control option, the calendar method isn't it. Most doctors suggest other forms of birth control methods before the calendar method because of both its high risk of unwanted pregnancy and lack of STI protection.

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