Patient: This could sound entirely ignorant, and I’m sure there’s a logical answer, but the information I find seems to be so inconsistent. Some say you have to be on the pill for a month in order for it to really be effective. Some say a week. Either way, you only have to be off the pill for a day for it to become ineffective. Why is there such a difference in the time frames for effectiveness versus ineffectiveness of birth control?
Doctor: The explanation is based on the mechanism of action and changes, birth control pills bring about, for effective contrace ption. Pills are an external supply of sex hormones that manage to suppress ovulation and the release of ovum. Also when the availability of these hormones is adequate in the body, the regulatory centres of the brain (that normally control the sex hormone secretion), stay temporarily inactive, as long as the external supply of hormones is uninterrupted. Now if you go off the pill, even once, the amount of available hormone, (depending on what phase of your cycle you missed your pill), will fluctuate and may activate the brain centre to trigger hormone production and ovulation. Thus ovum may be released anytime (cannot be sure of the time of ovulation since it was suppressed till now, and the time of release of ovum is uncertain until you resume regular periods, off the pills once again), that may cause pregnancy.