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AMERICAN JOURNAL OF OBSTETRICS AND GYNECOLOGY. 1992 Oct; 167(4 Pt 2):1171-6.The largest case control study on the association between oral contraceptive (OC) use and cancer is the US Cancer and Steroid Hormone (CASH) study. Since it did not use hospital-based patients as controls, it eliminated some biases. Since OCs suppress ovulation and suppressed ovulation is linked with reduced risk of ovarian cancer, scientists believe OCs may reduce this cancer risk. The CASH study shows that OC use indeed decreases the risk of ovarian cancer 40% (relative risk [RR]=.6 and this protection lasts for more than 10 years after OC discontinuation. Protection increases with duration of OC use (<1 year RR=.6 and >10 years RR=.2). Estrogenic stimulation of the endometrium without ample progestational protection causes endometrial cancer. Thus combined OCs which have estrogen and progestin components should reduce the risk of endometrial cancer. The CASH study reveals OC use for at least 12 months reduces this risk 50%. OCs have a protective effect for at least 15 years after stopping OC use. In addition, UK national mortality data show OC use caused the decline in ovarian cancer mortality and a 40% decrease in endometrial cancer mortality over the last 20 years. A WHO 7-county case control study indicates that OC users in developing countries have the same protective effect against ovarian and endometrial cancer as those in developed countries. Studies of OC use and cervical cancer have had conflicting results due to 3 biases: cervical cancer is associated with sexual behavior and is therefore a sexually transmitted disease; detection bias. A study in Costa Rica conducted by CDC study has addressed the 1st and 3rd biases. It found no increased risk of invasive cervical cancer or carcinoma in situ with OC use. Studies of OC use and breast cancer have also had conflicting results, but the data clearly indicate that OC use does not increase the overall risk of breast cancer. In fact, OC benefits surpass breast cancer risks.
Healthright. 1985 Aug; 4(4):9-12.The pattern of reproductive activity displayed by early hunter-gatherer ancestors, before the dawn of civilization, must have been vastly different from today's pattern. In the absence of contraception such women would have spent the greater part of their reproductive lives either pregnant or in lactational amenorrhea. In developing these ideas further it was estimated that a hunter-gatherer woman would have spent about 15 years in lactational amenorrhea, whereas just under 4 years would have been occupied by her 5 pregnancies, and she would only have had about 4 years of menstrual cycles. The total number of menstrual cycles she would experience in her entire life would be no more than about 50. This is in marked contrast to the situation today in a typical Western woman using contraceptives and experiencing menarche at 13 and the menopause at 50. Allowing her 2 years' respite from cycles during her 2 pregnancies, each followed by only a token period of breastfeeding, this leaves 35 years during which she would experience about 420 menstrual cycles. The conclusion is that an excessive number of menstrual cycles is an iatrogenic disorder of communities practicing any form of contraception. Thus, it is important to note that even the condom or vasectomy have important repercussions on the female's reproductive cycle. Since 99.9% of human existence has been spent living a nomadic hunter-gatherer life, this high frequency of menstrual cycles is a new experience, one that humans may be genetically ill-adapted to cope with. In fact, there are a number of "diseases of nulliparity" whose incidence is markedly increased in women with few or no children and who are therefore experiencing an increased number of menstrual cycles. These diseases include carcinoma of the breast, endometrium and ovaries, and endometriosis. As part of the effort to develop contraceptives that promote a healthy state of fertility, it is necessary to ask the question, "is a period really necessary?" To learn if women women accept a contraceptive method that reduced the frequency of menstruation, a clinical trial of an oral contraceptive was conducted. The OC was administered in such a way as to produce a withdrawal bleed only once every 3 months. This was termed the tricycle pill regimen. 196 women attending a family planning clinic in Edinburgh, Scotland, volunteered to participate, although 89 of them subsequently withdrew from the trial for a variety of reasons before it was completed at the end of a year. Overall, 82% of the women positvely welcomed the reduction in the number of periods; 91% of the women who completed the trial even refused to revert to a standard monthly OC regimen thereafter. The findings were in complete contrast to the results of a World Health Organization survey of patterns and perceptions of menstruation. But the WHO sample was highly biased in favor of women having regular menstrual cycles, and hence quite unrepresentative of the population as a whole. In sum, even the most pessimistic estimate of the WHO's menstruation survey shows that a proportion of women in every country investigated were prepared to accept amenorhea as a by-product of contraception. Reversible amenorrhea might become an increasingly popular form of contraception, and it might also confer significant health benefits.