Menstruation: How Do You Calculate Menstrual Cycle Length?

Question :

Is the menstrual cycle supposed to be 28 days from the first day of one period to the start of the next, or is it 28 days from the last day of one period to the start of the next?

Answer :

We count from the beginning of one period to the beginning of the next. Cycle day 1 is the first day of bleeding. A normal cycle length is between 23 and 35 days

To calculate menstrual cycle length, you count the number of days from day one of your period (CD=cycle day 1) up to, and including, the day before the next period starts.

The count does not include the first day of the next menstrual period, because that's Cycle Day 1 of the next cycle.

EXAMPLE: Period starts June 3rd, and lasts for 5 days. The next period starts June 27.

MENSTRUAL CYCLE LENGTH CALCULATION:

Count the number of days from June 3rd to June 26th. The counting includes June 3rd (CD 1), and also includes June 26th.

The start day of the next period, June 27, is not included as it starts the new cycle.

FINGER COUNTING SIMULATION FOR THIS EXAMPLE (1, 2, 3...)

ANSWER FOR THIS EXAMPLE: Cycle Length = 24 days

Note: The period length of 5 days does not effect the cycle length calculation. Had this period been 4 days or 6 days, cycle length would still be 24 days.

AVERAGE CYCLE LENGTH:

Average cycle length, in turn, is calculated by summing up each individual cycle length and dividing by the total number of cycles.

The chart below places the female menstrual cycle into a circular format similar to the dial dispenser for oral contraceptives. You will have to cross reference to the diagram to the left to integrate the information about the changes in anterior pituitary = adenohypophyseal hormones and ovarian hormones respectively.

This article was taken from:yourtotalhealth.ivillage whenmybaby yahooimages apsu.edu