Calendar-based contraceptive methods: Difference between revisions

Revision as of 14:59, 2 October 2006

Revision as of 21:35, 2 October 2006

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To find the estimated length of the pre-ovulatory infertile phase, nineteen (19) is subtracted from the length of the woman's shortest cycle. To find the estimated start of the post-ovulatory infertile phase, ten (10) is subtracted from the length of the woman's longest cycle.<ref>Kippley, John and Sheila Kippley. ''The Art of Natural Family Planning.'' The Couple to Couple League, Cincinnati, OH: 1996. p.154. ISBN 0-926412-13-2</ref>

A woman whose menstrual cycles ranged in length from 30 to 36 days would be estimated to be infertile for the first 11 days of her cycle (30-19=11), to be fertile on days 12-25, and to resume infertility on day 26 (36-10=26). When used to avoid pregnancy, the Rhythm Method has a perfect-use failure rate of up to 9% per year.<!--

--><ref name="hatcher">{{cite book | first=RA | last=Hatcher | coauthors=Trussel J, Stewart F, et al | year=2000 | title=Contraceptive Technology | edition=18th Edition | publisher=Ardent Media | ___location=New York | id=ISBN 0-9664902-6-6 | url=http://www.contraceptivetechnology.com/table.html }}</ref>

===Standard Days Method===

The Standard Days Method may only be used by women whose cycles are always between 26 and 32 days in length. In this system, days 1-7 of a woman's menstrual cycle are considered infertile. Days 8-19 are considered fertile. Infertility is considered to resume beginning on day 20. When used to avoid pregnancy, the Standard Days Method has a perfect-use failure rate of 5% per year.<!--

--><ref>{{cite journal | author = Arévalo M, Jennings V, Sinai I | title = Efficacy of a new method of family planning: the Standard Days Method. | journal = Contraception | volume = 65 | issue = 5 | pages = 333-8 | year = 2002 | id = PMID 12057784 | url=http://pdf.dec.org/pdf_docs/PNACQ416.pdf}}</ref>

===Imperfect use===

Imperfect use of the Rhythm Method would consist of not correctly tracking the length of the woman's cycles, thus using the wrong numbers in the formula, or of having intercourse on an identified fertile day. Imperfect use is fairly common, and the actual failure rate of the Rhythm Method is 25% per year.<!--ref name="hatcher" />

--><ref>James Trussell et al.[http://www.plannedparenthood.org/pp2/portal/files/portal/medicalinfo/birthcontrol/pub-birth-control-02.xml Contraceptive effectiveness rates]. Contraceptive Technology — 18th Edition, New York: Ardent Media. On-press, 2000.</ref>

==Reasons for high failure rate==