Figure 174.1. A 28-day menstrual cycle.

Figure 174.1

A 28-day menstrual cycle. Not all cycles are 28 days long. It is the phase before ovulation that varies in length. (Courtesy of Contraceptive Technology.)

From: Chapter 174, Birth Control

Cover of Clinical Methods
Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition.
Walker HK, Hall WD, Hurst JW, editors.
Boston: Butterworths; 1990.
Copyright © 1990, Butterworth Publishers, a division of Reed Publishing.

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.