The combined oral contraceptive pill and the assumed 28-day cycle

Abstract

Some studies involving women taking the combined oral contraceptive pill (COCP) have on occasion assumed the COCP group to have a rigid 28-day pharmaceutically driven cycle. Anecdotal evidence suggests otherwise, with many women adjusting their COCP usage to alter the time between break-through bleeds for sporting and social reasons. A prospective field study involving 533 scuba diving females allowed all menstrual cycle lengths (COCP and non-COCP) to be observed for up to three consecutive years (St Leger Dowse et al. 2006). A total of 29% of women were COCP users who reported 3,241 cycles. Of these cycles, only 42% had a rigid 28-day cycle, with the remainder varying in length from 21 to 60 days. When performing studies involving the menstrual cycle, it should not be assumed that COCP users have a rigid confirmed 28-day cycle and careful consideration should be given to data collection and analysis. The effects of differing data interpretations are shown.

Turkish recreational divers: a comparative study of their demographics, diving habits, health and attitudes towards safety

“…33 This differs from European countries, where the rate of OCP use among divers is similar to or higher than the general female population (around 30%). 9,34,35 The low use of OCPs among Turkish females is not unexpected, and is explained by cultural differences; traditional contraceptive methods are commoner in Turkey. 33 However, the fact that OCP use in divers is half that of the general population is surprising; this trend has only been reported in one other country (Australia; 9% in divers, 30% in the general poulation), but their uptake is still much higher than in Turkish female divers.…”