Birth control pills: new scientific evidence supporting natural estrogens

By analyzing adverse event reports recorded in the U.S. Food and Drug Administration’s pharmacovigilance database, researchers at UNamur have shown that certain birth control pills containing estrogens more similar to those naturally produced by the body, such as 17β-estradiol or estetrol, were associated with fewer reports of blood clots than pills containing ethinylestradiol, a synthetic estrogen that has been widely used for several decades. Furthermore, the rates observed with these new generations of contraceptives were similar to those reported for progestin-only pills, which are considered the safest in terms of cardiovascular risk.

This study confirms data collected by the same team in EudraVigilance, the European database for managing and analyzing reports of adverse drug reactions, and published in 2025 in the journal Contraception.

The findings of this research send an important message regarding public health, as the pill is used by millions of women worldwide. These results call for a reevaluation of certain prescribing practices in favor of options with a more favorable or even neutral thrombotic profile. This contribution is all the more crucial today, as more and more people are turning away from contraceptives or hormone replacement therapies, which are nonetheless essential for public health.

“Our goal is to shift the landscape of prescribing guidelines. Biological and observational evidence supporting formulations based on natural estrogens is growing. These data show us that safer alternatives exist; it is time to reverse the trend. ” — Lucie Raskin, Researcher in the Department of Pharmacy.

Beyond the findings themselves, this publication highlights the role of Belgian academic research in a field with significant societal impact. Through this work, Lucie Raskin embodies a new generation of researchers committed to addressing concrete issues in women’s health, while Jonathan Douxfils contributes the scientific and clinical expertise he has developed over several years on the links between hormones, coagulation, and thrombotic risk. This expertise now extends beyond the local context and is part of a European and international effort, particularly through Jonathan Douxfils’ participation in several international expert networks dedicated to contraceptive safety and the assessment of hormone-related thrombotic risk.

While venous thrombosis is the most serious complication associated with hormonal contraceptive use, other aspects are also beginning to be studied by the scientific community, particularly in terms of bone health and mental health. Regarding the risks of breast cancer, here too, the data are currently being updated and show favorable profiles depending on the progestin used.

This research demonstrates that more informed contraceptive choices are possible and that better use of scientific knowledge can improve prevention, reduce serious complications, and promote more personalized medicine in the field of women’s health. 

• Birth Control Pills: Assessing the Risk of Thrombosis for Safer Prescribing 
• Safer oral contraceptives thanks to natural estrogens