There is ALWAYS a possibility of pregnancy with the pill - something like 2% chance. Once one has build up a level of the pill in their system (or the active ingredient) then there is an extended period of time after the last dose that the effectiveness is high enough to be considered a "contraceptive". However the greater the time after the last one the higher the risk of pregnancy. In the first couple of days you slowly creep up the risk factor. 2% becomes 3% then 4% then 6%... up and up over a period of time. BUT that does not mean you will get pregnant, it only means that odds are improving in that direction. In the opposite direction, many women discover it takes months for them to "get back to normal" when it comes to menstruation and flow, they also discover that there is a longish period of time the pill were their fertility is reduced. But then there are those women who get pregnant even when following dosing schedule religiously. Brand Versus Type: There are several different types of 'The Pill' out there now. Thus one must be careful or review with one's doctor the risks of pregnancy between the stopping of one type of contraceptive pill and the start of another. Brand V Generic may only mean 0.01% adjustment in the risk. so low that it basically doesn't matter. However Generic may be mixed with other chemicals (for color, for binding agents) which have shown to have a minor effect on effectiveness of the medication for SOME patients. There is also evidence of a fairly high placebo effect for many patients when it comes to the differences between Generic and Name Brand. The Placebo Affect appears to be that if you believe Generic is not as good as Name Brand then you most likely will get less benefit from the generic brand. Granted one would think this should not affect something like birth control, but it does - other behaviors change (such as when the pill it taken) that have an impact on the effectiveness of the pill. More often then not "I forgot" plays a huge roll in those cases. When it comes to using The Pill for other "womanly issues" The placebo effect become much larger.