0
We're unable to sign you in at this time. Please try again in a few minutes.
Retry
We were able to sign you in, but your subscription(s) could not be found. Please try again in a few minutes.
Retry
There may be a problem with your account. Please contact the AMA Service Center to resolve this issue.
Contact the AMA Service Center:
Telephone: 1 (800) 262-2350 or 1 (312) 670-7827  *   Email: subscriptions@jamanetwork.com
Error Message ......
ARTICLE |

The Length and Variability of the Human Menstrual Cycle

Leonard Chiazze Jr., ScD; Franklin T. Brayer, MD; John J. Macisco Jr., PhD; Margaret P. Parker, MS; Benedict J. Duffy, MD
JAMA. 1968;203(6):377-380. doi:10.1001/jama.1968.03140060001001.
Text Size: A A A
Published online

The Center for Population Research collected 30,655 recorded menstrual cycles from 2,316 women. Ninety-five percent of all cycles were between 15 and 45 days long. The mean and standard deviations for the total number of cycles were 29.1 and 7.46, respectively. Cycle lengths between 15 and 45 days averaged 28.1 days with a standard deviation of 3.95 days. Variability of menstrual-cycle lengths is highest for women under 25 years of age and declines steadily to reach a minimum for ages 35 to 39. It is then followed by a slight increase for women aged 40 to 44. The pattern of variability by age is demonstrated equally well by the percent of cycles between 25 and 31 days in length as by the standard deviation.

Topics

Sign in

Create a free personal account to sign up for alerts, share articles, and more.

Purchase Options

• Buy this article
• Subscribe to the journal

First Page Preview

View Large
First page PDF preview

Figures

Tables

References

CME
Also Meets CME requirements for:
Browse CME for all U.S. States
Accreditation Information
The American Medical Association is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The AMA designates this journal-based CME activity for a maximum of 1 AMA PRA Category 1 CreditTM per course. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Physicians who complete the CME course and score at least 80% correct on the quiz are eligible for AMA PRA Category 1 CreditTM.
Note: You must get at least of the answers correct to pass this quiz.
Your answers have been saved for later.
You have not filled in all the answers to complete this quiz
The following questions were not answered:
Sorry, you have unsuccessfully completed this CME quiz with a score of
The following questions were not answered correctly:
Commitment to Change (optional):
Indicate what change(s) you will implement in your practice, if any, based on this CME course.
Your quiz results:
The filled radio buttons indicate your responses. The preferred responses are highlighted
For CME Course: A Proposed Model for Initial Assessment and Management of Acute Heart Failure Syndromes
Indicate what changes(s) you will implement in your practice, if any, based on this CME course.

Multimedia

Some tools below are only available to our subscribers or users with an online account.

Sign in

Create a free personal account to sign up for alerts, share articles, and more.

Purchase Options

• Buy this article
• Subscribe to the journal

Related Content

Customize your page view by dragging & repositioning the boxes below.

Jobs
brightcove.createExperiences();