The most common contraceptives that contain oestrogen are so-called combined pills, which, besides preventing pregnancy, also aim to mimic a woman’s menstrual cycle as closely as possible. They are available in the form of monophasic, biphasic, triphasic and quadriphasic pills. The monophasic pill contains a fixed dose of oestrogen and progestogen, while the multiphasic pills contain varying doses. Monophasic pills are the ones most commonly prescribed.
Oestrogen and the risk of thrombosis
Contraceptives that contain oestrogen normally increase the risk of thrombosis (blockage of a blood vessel by a blood clot). The absolute risk is relatively small; every year around 5 to 12 women in every 10,000 (who are taking contraceptives that contain oestrogen) develop thrombosis.
Contraceptives that contain oestrogen and the benefit of DNA analysis
The risk of developing thrombosis if you take contraceptives that contain oestrogen varies from one individual to another. The risk of thrombosis increases if you have high blood pressure, smoke, are older or overweight, have poor circulation, suffer from cardiac arrhythmia or have a hereditary defect.
If you have a hereditary defect, your blood does not stop clotting as effectively as it should or levels of substances that stimulate clotting are too high in the body. This significantly increases the risk of thrombosis. Two relatively common hereditary defects are Factor V Leiden (F5 gene) and Factor II (F2 gene). Rare defects in the SERPINC1, PROC and PROS1 genes have also been described.
A preventive pharmacogenetic DNA analysis can therefore be an important tool when it comes to deciding on a suitable contraceptive.
Contraceptives that contain oestrogen and the genes F5, F2, SERPINC1, PROC, and PROS1
Your individual risk of thrombosis if you take contraceptives that contain oestrogen (the pill) may be partly explained by genetic variations. It is known, for example, that variations in the F5, F2, SERPINC1, PROC and PROS1 genes are partly responsible.
One specific variation in the F5 gene is relatively common in Europe: it is present in around 3 to 8% of people (this mutation is rare in Asia and Africa). Variations in the SERPINC1, PROC and PROS1 genes are rare. The specific variation in the F2 gene is found in around 2% of Europeans (in Southern European countries it occurs more frequently).
Information about your genetic predisposition may therefore provide grounds for extra vigilance in relation to contraceptives that contain oestrogen.
Read more about Factor V Leiden, F2, SERPINC1, PROC, PROS1 »