It is critical to understand the normal physiological and anatomical changes during the menstrual cycle in order to understand the NFP methods and to identify disease. Cervical mucus is the most important determinant of fertility and is used as an effective marker of locating when ovulation occurs. NFP methods measure changes in symptoms such as cervical mucus and body temperature to locate periods of fertility/infertility within a cycle. Mucus usually changes from sticky, thick, opaque to lubricative, thin, clear and stretchy, then returns back briefly to sticky, thick and opaque.
In addition to indicating fertility, the menstrual cycle provides valuable information on a woman’s overall health status, reasons for an irregular cycle and potential co-morbidities. There are several causes of menstrual cycle irregularity which can be identified with close observation, charting and additional testing. A certain degree of variability is normal, but large variations sustained over multiple cycles may indicate further investigation. The great thing about NFP is that it is based on the symptoms of each woman’s cycle and therefore the results are very meaningful for interpreting fertility and health status.
References: 1) Wilcox AJ, Dunson D, Baird DD. The Timing of the Fertile Window in the Menstrual Cycle: Day Specific Estimates from a Prospective Study. BMJ. 2000;321(7271):1259-62. 2) Breech L, Diaz A, Hertwick SP, Hillard PA, Laufer M. American Academy of Pediatrics Committee on Adolescence. 2006;349:1-6.3) Wikipedia, Diagram of the Menstrual Cycle, Image. 2013. Available at: http://en.wikipedia.org/wiki/File:MenstrualCycle2_en.svg accessed on June 18, 2013.
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