Contraceptive use in women may increase the risk of blood clot. Experts study indicates, the use of non-oral hormonal contraceptives like the patch, implants and vaginal rings may cause a higher risk of blood clot (known as venous thromboembolism) than oral contraceptives.
Several previous studies indicate a risk of venous thrombosis (collective form of deep vein thrombosis and pulmonary embolism) in women who use birth control pills or oral contraceptives. But, there are still very few studies that look at the risk of non-oral hormonal contraceptives.
In his study, Professor Ojvind Lidegaard of University of Copenhagen Denmark and his team examined a variety of research data related to the use of non-oral hormonal contraceptives to the risk of venous thrombosis in non-pregnant women (15-49 years) in Denmark during 2001-2010. All women involved in the study had no history of either blood clots or cancer before the study began. Several factors can affect the results of these findings, such as age and education level.
The study found during the period 2001 to 2010, there were about 3434 women that were diagnosed have venous thrombosis. The risk of women who were not using hormonal contraception and aged between 15-49 years is only two cases in 10,000 years of exposure. Women who use combination birth control pills containing the hormone levonorgestrel had a three-fold increased risk (6.2 events per 10,000 years of exposure).
When compared with women who used non-oral hormonal contraceptives (the same age), women using the patch / patches have an eight times increased risk (9.7 events per 10,000 years of exposure), while women using the vaginal ring has 6.5 times increased risk (7.8 events per 10,000 years of exposure).
This study was published in British Medical Journal online edition on May 10, 2012. The use of implants containing progestogen, tend to have a very small risk of blood clots. There is no risk for women using progestogen and may even have a protective effect.
Researchers saw no reduction in risk in women using the patch or vaginal ring in the long run. Based on these findings, the researchers estimate that 2,000 women using the vaginal ring and 1,250 women using the patch should switch to using combination birth control pills that contain levonorgestrel to prevent the incidence of venous thrombosis in one year.
"Women should be informed of this risk in order to select the most appropriate hormonal contraceptives," said Lidegaard.
"There is a hormonal contraceptive alternatives that provide less risk or none at all to the development of venous thrombosis," he added.
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