Oestrogen component of COCs: have we finally found a replacement for ethinyl estradiol?

PURPOSE OF REVIEW: Combined oral contraceptive pills are among the most widely used contraceptive methods globally. Despite their popularity, the potential risks and side effects can lead to both high discontinuation rates and adverse outcomes including thromboembolic events. The quest for a safer alternative to the traditional ethinyl estradiol/progestin combination has led to the use of newer oestrogens. Ethinyl oestradiol alternatives will be reviewed including the newest option, estetrol, as it enters clinical use.

RECENT FINDINGS: Oestradiol, when combined with a progestin with strong endometrial activity, is a viable alternative to ethinyl estradiol in the form of oestradiol valerate and estradiol, which have been available since 2008 and 2011, respectively. Estetrol is the newest oestrogen available and is found naturally in the foetal liver. Estetrol was approved for use in 2021. All three of these alternatives have high contraceptive efficacy, similar if not improved cycle control and decreased impact on haemostatic factors as compared to ethinyl estradiol.

SUMMARY: Alternatives to ethinyl oestradiol, including the newest option of estetrol, show promise in providing comparable contraceptive efficacy with potentially lower risk of side effects and thromboembolic events.