L5.2.4.1.2.2: Calendar/Rhythm Method

• Calendar/Rhythm Method

  ❖ Safe and fertile days are calculated by tracking the length of menstrual cycles over several months.
• FIRST, DETERMINE THE LENGTH OF THE MENSTRUAL CYCLE

  Step 1:

  Record the lengths of the menstrual cycle for at least 6 periods/months.

  Step 2:

  Mark the 1st day of your period as day 1.

  Step 3:

  Mark the 1st day of the next period.

  Step 4:

  Count the total number of days between each cycle. (The number of days between the first days of each period)
• Example: Your period started on October 31, and your next period started on November 29. Counting the days (including Oct 31) until the day BEFORE the next period started (Nov 28) = The cycle length of the month is 29 days.

  
• SECOND, PREDICT THE FIRST FERTILE DAY

  Step 5:

  Find the shortest cycle in the past record.

  Step 6:

  Subtract 18 from the total number of days in that cycle.

  Step 7:

  Count that number from day 1 of the current cycle and mark that day with an X. (Include day 1 when you count).

  Example: The shortest cycle in the chart is 26 days (For the Month of MAY).

  26 DAYS - 18 = 8

  
• THIRD, PREDICT THE LAST FERTILE DAY

  Step 8:

  Find the longest cycle in the past record.

  Step 9:

  Subtract 11 from the total number of days in that cycle.

  Step 10:

  Count that number from day 1 of the current cycle and mark that day

  with an X. (Include day 1 when you count)

  Example: The longest cycle in the chart is 30 days (For the Month of JULY)

  30 DAYS - 11 = 19

  
• Example: In the month of October, your period started on Oct 4.

  ● Counting 8 days from that day, Oct 11 is the beginning of the FIRST FERTILE day.

  ● Counting 19 days from the same day (Oct 4), Oct 22 is considered as the LAST FERTILE day.

  
• Criteria To Use

  Applicable only for a 26-35 days cycle.
• First and Last Fertile Days

  First Fertile Day = Length of Shortest Cycle - 18

  Last Fertile Day = Length of Longest Cycle - 11
• EFFECTIVENESS OF THE RHYTHM METHOD:

  It is effective 75% of the time. It isn't as effective at preventing pregnancy as other methods, such as taking birth control pills or using an intrauterine device (IUD).