New Study on contraception and arterial thrombosis

A new large Danish study assessing the influence of different types of hormonal contraception on the risk of arterial thrombosis (thrombotic stroke and myocardial infarction) is published today.

A new Danish study including 1.6 million Danish women 15-49 years old has been published in the New England Journal of Medicine. The study finds that the risk of cerebral and heart thrombosis has diminished by the reduction in oestrogen dose of oral contraceptives, and that these products generally have less influence on arterial thromboses than on venous thrombosis (thrombosis of leg or lung).

Read the study here

The new study was planned and conducted by Professor Øjvind Lidegaard, Gynaecological Clinic, Rigshospitalet and associate Professor Ellen Løkkegaard, Hillerød Hospital.

What are the important new findings in the study?

“The study is the largest ever conducted on the influence of hormonal contraception on the risk of arterial thrombosis. More than 5,000 young women with these diseases participated in the study. And the study is the only one assessing the risk of a long list of new hormonal contraceptive products launched over the last decade”, says Professor Lidegaard.

“The study shows that combined oral contraceptives with 20µg oestrogen increase the risk of arterial thrombosis with about 50%, and combined pills with 30-40 µg oestrogen increase the risk with 80%. But also that progestogen only products, such as hormone-IUD, progestogen only pills, and subcutaneous implant, don’t confer any increase in the risk of arterial thrombosis. Women with risk factors of thrombosis are therefore recommended to use these latter products.”

The study has merged data from five national registries, and follows 1.6 million women of fertile age from 1995 through 2009, all free of pervious thrombotic and malignant disease. The analysis includes adjustments for treatment of hypertension, diabetes, hyperlipidaemia, heart diseases, and smoking.

Lidegaard continues: “In the other end of the risk spectrum, transdermal patches and vaginal ring more than double the risk of arterial thrombosis, the same two products with the highest risk of venous thrombosis. Therefore, these products should only be used after informed consent.
In contrast to venous thrombosis, we didn’t find major differences in risk of arterial thrombosis between hormonal contraceptive products with different progestogens. Thus, for the same dose of oestrogen, we found approximately the same risk of thrombotic stroke and myocardial infarction for 2nd, 3rd, and 4th-generation combined pills” concludes Professor Lidegaard.

Contact Professor Lidegaard:  
Mail: Lidegaard@rh.regionh.dk
or by telephone: +45 4063 2268