Calendar-based contraceptive methods: Difference between revisions

Revision as of 21:35, 2 October 2006

Revision as of 00:22, 4 October 2006

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The Rhythm Method formula makes several assumptions that are not always true.

The postovulatory ([[Menstrual cycle#Luteal phase|luteal]]) phase has a normal length of 12 to 16 days,<ref>Weschler, Toni. ''Taking Charge of Your Fertility.'' HarperCollins, New York: 2002. p.48 ISBN 0-06-039406-4</ref>, and the Rhythm Method formula assumes all women have luteal phase lengths within this range. However, many women have shorter luteal phases, and a few have longer luteal phases.<!--ref>Kippley, p.111</ref> For these women, the Rhythm Method formula incorrectly identifies a few fertile days as being in the infertile period.

--><ref>Kippley, p.111</ref>. For these women, the Rhythm Method formula incorrectly identifies a few fertile days as being in the infertile period.

The Rhythm Method uses records of past menstrual cycles to predict the length of future cycles. However, the length of the pre-ovulatory phase can vary significantly, depending on the woman's typical cycle length, stress factors, medication, illness, [[menopause]], [[breastfeeding]], and whether she is just coming off [[hormonal contraception]]. If a woman with previously regular cycles has a delayed ovulation due to one of these factors, she will still be fertile when the Rhythm Method tells her she is in the post-ovulatory infertile phase. If she has an unusually early ovulation, the Rhythm Method will indicate she is still in the pre-ovulatory infertile phase when she has actually become fertile.