The method of reducing the risk of pregnancy by restricting penetrative sexual intercourse with ejaculation to times when fertility is believed to be minimal because of the phase of the menstrual cycle. In theory, a woman is least likely to conceive during her menstrual period or shortly before and after her period. The critical word is the adverb “shortly” because ovulation can occur late or early rather than in the middle of the menstrual cycle, and it is believed that some women ovulate under the stimulus of orgasm. A refinement of the rhythm method is to record temperature fluctuations because a slight rise may accompany rupture of the Graafian follicle and release of an ovum from the ovary. However, even with this refinement, the rhythm method, advocated as the only acceptable method for Roman Catholics who adhere to papal pronouncements, is unreliable.
Subjects: Public Health and Epidemiology.