This was due to the effect of oestrogen on the synthesis of clotting factors. However, an association between the pill and venous thromboembolism soon emerged. The first available formulation of the combined oral contraceptive pill contained 50 microgram of ethinyloestradiol for cycle control. Table 1- Combined oral contraceptive pills 3 More recent developments, which may improve the safety and efficacy of the combined oral contraceptive pill, include using oestradiol instead of ethinyloestradiol and extended pill regimens with fewer or no inactive pills. 2 However, there may be an increase in unscheduled bleeding. 1 Subsequently it has been found that formulations with ethinyloestradiol 20 microgram are likely to be as effective as the 30–35 microgram pills while possibly reducing the oestrogenic effects such as nausea, bloating and breast tenderness. Since then the pill has been further developed to ensure good efficacy while minimising the adverse effects.Ī key advance was a decrease in the dose of oestrogen to the currently used low-dose formulation (standard dose of ≤ 35 microgram ethinyloestradiol). Women rapidly adopted the pill as it allowed the reliable separation of sex and reproduction and gave them the opportunity to plan when to have children. Australia was the second country in the world to have access to 'the pill'. It was introduced into Australia just over 50 years ago.

The combined oral contraceptive pill contains oestrogen and progestogen.

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