Break-through bleeding

Progestagens used alone inhibit ovulation in up to 40% of cycles, render cervical mucus less easily penetrable by sperm and induce a premature secretory change in the endometrium so that implantation does not occur. There is liable to be break-through bleeding and some are a cause of raised blood pressure and an adverse trend in blood lipids and arterial disease. 

CSM in the UK for the years 1968 to 1984 (61 cases were attributed to other antibacterials). Another survey of oral contraceptive failure identified 1 failure due to erythromycin (48 of209 pill failures were attributed to antibacterials), and break-through bleeding due to erythromycin has also been described in 2 cases. Conversely, in 2 studies of contraceptive failures in dermatology patients, no pregnancies were identified in a total of 74 women taking erythromycin and an oral contraceptive. ... 

Another way to examine the effeet of earbon partiele size on kineties is to look at the bleed emissions from a earbon eanister [20,35]. Bleed emissions are those emissions that oecur prior to break through. They are the result of the diffusion of gasoline vapor components that ean develop during extended soak times between purge and adsorption events. 

Hydrocarbon vapor migration within the carbon canister is a significant factoi during the real time diurnal test procedure. The phenomenon occurs after the canister has been partially charged with fuel vapors. Initially the hydrocarbons will reside primarily in the activated carbon that is closest to the fuel vapor source. Over time, the hydrocarbons will diffuse to areas in the carbon bed with lower HC concentration. Premature break through caused by vapor migration for twc different canisters is shown in Fig. 17. The canister with the L/D ratio of 5.0 shows substantially lower bleed emissions than the canister with an L/D ratio of 3.0. 

Effect on menstruation (it is not true menstruahon, see above) is generally to regularise it, and often to diminish blood loss, but amenorrhoea can occur. In some women break-through intermenstrual bleeding occurs, especially at the outset, but this seldom persists for more than a few cycles. Premenstrual tension cind dysmenorrhoea are much reduced. 

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