Rhythm Method of Birth Control | How to do it the safe way

At NaturalContra we think it’s important that women know of the rhythm method even though it is not one of the methods that we recommend.

It is not a safe natural birth control method, but keep reading to learn more about this method and how it can be made safe.

What is the Rhythm method, also known as the calendar method

The rhythm method of birth control involves a woman assuming her safe days based on her history and avoiding sexual activity – or using unnatural birth control methods, such as condoms – during her predicted fertile window (unsafe days).

History and prediction

To use the rhythm method, you need to predict your fertile period based only on your menstrual cycle history. Your fertile period is when you’ll be ovulating, and a few days immediately before that.

Because this fertile period means you are more likely to conceive, it is also the time to avoid unprotected sex to prevent pregnancy. You may also want to avoid sexual activity altogether if you don’t want to use a barrier method* of birth control.

*Barrier methods create a barrier between the sperm and the uterus, e.g. male and female condoms, diaphragm and sponges.

rhythm method

We do not consider the rhythm method a safe natural birth control method, but keep reading to learn more about this method and how it can be made safe.

How the rhythm method works

  1. You start by recording the length of at least 6 of your menstrual cycles.
  2. Using a calendar, write down the number of days in each menstrual cycle – count from the first day of your period to the first day of your next period.
  3. You take note of the length of your shortest menstrual cycle.
  4. Subtract 18 from the total number of days in your shortest cycle. This is the first fertile day of your cycle. 
  5. Take note of the length of your longest menstrual cycle.
  6. Subtract 11 from the total number of days in your longest cycle. This is the last fertile day of your cycle. 
  7. You’ve found your fertile days.
  8. To avoid pregnancy, don’t have unprotected vaginal intercourse during your fertile days.

Why is the rhythm method not safe to use?

We don’t recommend the rhythm/calendar method because it doesn’t work under conditions that are common for many women:

  • If you have irregular menstrual cycles
  • If you had your first period recently
  • If you had a baby recently
  • If you stopped taking birth control pills recently or other forms of hormone contraceptives
  • If you’re breastfeeding
  • If you’re approaching menopause

The calendar method has a 76 percent effectiveness rate, which means it’s not reliable. It’s unsafe because menstrual cycles can be irregular even if most of the time they are not. Medications, illness and even stress can affect the timing of your ovulation and alter even the most regular of cycles.

rhythm method

Positive aspects of the rhythm method

Unlike medical methods of birth control, like the pill, the rhythm method doesn’t have side effects. These are the main benefits of using this natural method of birth control.

  • No side effects
  • No contraindications regarding pre-existing conditions
  • No possible interaction with other medications
  • No religious objections
  • Inexpensive

Having said that, the rhythm method is not safe enough to count on. Moreover, all other natural methods of birth control share these positive aspects as well.

How to use the rhythm method the safe way?

The only safe way to use the rhythm method is by using it with fertility monitors. They that your basal body temperature, the electrolytes levels in your body or levels of hormones in your urine. This will allow you to know your actual fertile window for sure, without any guessing.

rhythm method


Today we learned that the calendar method is not a safe form of birth control. It’s particularly unsafe for women with irregular periods. But the reality is that most women are prone to irregular menstrual cycles.

Therefore, the only way we are able to recommend the rhythm method is if you combine your calendar with a fertility monitor. This way, the effectiveness of your birth control can be up to 99.4%! That means it becomes more reliable than condoms, isn’t that amazing? ?

Let me know what you think in the comments below!

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