birth-control, contraceptivesEven when used perfectly, oral contraceptives are not completely effective. (Wikipedia’s article says the failure rate is 0.3%.) Though the normal menstrual cycle is simulated, the hormonal cycle is presumably very different while on the pill; does this mean that failures do not tend to follow the normal fertility cycle? Is it completely impossible to combine any sort of calendar-based method with the pill?
No, as I understand it; women menstruate after their hormonal level crashes. The pill simulates this hormonal crash by fooling the woman’s body during the first 3 weeks of the cycle to think it is pregnant (Progesterone?), and then during the period week, the hormone goes away and frequently the week off pill is either just sugarpill, or is an iron supplement (since people get a bit anaemic during times of heavy bleeding).
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