Pregnancies in reliable pill takers.

This study is an extension of a previous study on oral contraceptive pill method failure in reliable pill takers. It documents 137 cases which presented during the 3 year period from December 1985 to December 1988. The most important new finding is that smoking is a significant risk factor in failure on the combined pill (67% were smokers, n = 118), but not on the progestagen-only pill, although the numbers in the latter group were small (n = 19). Diarrhoea and/or vomiting (46%) and drug interactions (33%) are confirmed as important predisposing factors. Systemic illness and/or severe psychological stress may also affect pill utilisation and such factors were found in 47%. Menstrual disturbances were found in 32% of women on the combined pill and 68% of these were smokers. Multiple factors were present in most cases (79%). Repeat failures occurred in 25%.