The calendar rhythm method is a calendar based contraceptive method which is suitable for women with irregular menstrual cycles, or those which last less than 26 or more than 32 days.
The menstrual cycle refers to the cyclic events which occur in a woman’s ovaries and uterus to prepare them for reproduction including development of the uterine lining, ovulation (release of a mature egg) and shedding of the menstrual lining (menstrual bleeding. They typically occur in 28 day cycles which commence on the first day of menstrual bleeding. However, in some women cycle length may be as short as 21 days or as long as 40 days.1
For more information about the menstrual cycle see Menstruation.
Use the Calendar Rhythm Methods tool to calculate the times at which you are fertile and can get pregnant (and the times when you are not fertile). The calendar rhythm method is a calendar based contraceptive method which is suitable for women with irregular menstrual cycles, or those which last less than 26 or more than 32 days.
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- Marieb EN, Hoehn KN. Anatomy and Physiology (3rd edition). San Francisco: Pearson Benjamin Cummings; 2008. [Book]
For more information on contraception, including types of contraception, protecting against sexually transmitted infections, and contraception after childbirth, see Contraception (Birth Control).
For more information about pregnancy planning, including the importance of nutrition before pregnancy, being under-weight, being overweight, tobacco exposure, and alcohol consumption, see Pregnancy Planning (Preconception Advice).