Women taking the new-generation contraceptive pills Yaz, Yaz-Flex and Yasmin could have an increased risk of developing blood clots. By Joanna Egan
It is well-known that taking the combined oral contraceptive pill (the Pill) increases your risk of developing venous thromboembolism (VTE). This is a rare but serious condition that occurs when a blood clot forms inside a blood vessel. Commonly, they form in the leg (referred to as deep vein thrombosis). A blood clot can block the blood vessel, causing serious health complications, or it can dislodge and travel to the heart, brain or lungs. This can cause heart attack, stroke, breathing difficulties and sudden death. In every 10,000 women who take the Pill, between four and six will develop a blood clot.
Recent media reports suggest that oral contraceptives containing the progestogen drospirenone could carry a higher risk of VTE than other pills.
What is drospirenone?
Drospirenone is a relatively new version of the hormone progestogen. In Australia, it is found in the oral contraceptives YaZ, YaZ-Flex and Yasmin. These pills are as effective at preventing pregnancy as other oral contraceptives – if used correctly, they are about 99.7% effective. They work by stopping ovulation (the release of an egg from the ovary); thickening cervical mucus so sperm can't enter the uterus (womb); and changing the lining of the uterus to make it unsuitable for pregnancy.
Yasmin was launched in Australia in 2002, followed by Yaz in 2008. Yaz-Flex is a new version of Yaz that is designed to be taken continuously for four months in order to prevent monthly breakthrough bleeding. It became available in 2012. An estimated 200,000 Australian women take these oral contraceptives. They are said to be effective at reducing acne and improving symptoms associated with menstruation, such as bloating, swelling and weight gain related to fluid retention. They are not listed on the Pharmaceutical Benefits Scheme (PBS), costing approximately $25-30 per month.
Are Yaz, Yaz-Flex or Yasmin dangerous?
In 2011, two studies published in the British Medical Journal reported a greater risk of VTE in women taking oral contraceptives containing drospirenone compared to older generation pills, which contain a progestogen known as levonorgestrel. This prompted Australia's medicines watchdog, the Therapeutic Goods Administration (TGA), to issue a safety alert about the potentially increased risk these pills carry.
In September of this year, a further study was published in the British Medical Journal which reviewed thousands of pieces of published evidence and analysed 26 studies on the risk of VTE and oral contraceptives. The study concluded that, compared to non-users, the risk of VTE in users of oral contraceptives containing drospirenone was 3.8 fold. This was compared to a 2.8 fold risk of VTE in users of oral contraceptives containing levonorgestrel.
These findings contradict those of earlier studies, which found no additional risk. There has been rigorous debate surrounding the conflicting results. One possible reason for the discrepancies is that the earlier studies did not consider characteristics such as the participant's age, smoking status and body mass index. These are also risk factors for VTE.
Since the 2011 alert, the TGA has worked with the company that manufactures the pills to ensure the product information and consumer medical information is up-to-date and includes information about the risks.
What should women currently taking Yaz, Yaz-Flex or Yasmin do?
These women are advised to continue taking their oral contraceptive pills as normal and contact their health professional if they have any concerns. If they develop any symptoms of blood clots, such as persistent leg pain, severe chest pain, or shortness of breath, they should see their doctor immediately or go to the emergency department at their nearest hospital.
If women are concerned about their risk of developing VTE, they can ask their doctor about other methods of contraception. Alternatives include oral contraceptives with a lower VTE risk (those containing the progestogen levonorgestrel) or Mirena, a hormonal intra-uterine device (IUD) which releases a steady, low dose of levonorgestrel directly into the uterus. Women may also like to consider non-hormonal methods such as condoms, diaphragms, non-hormonal IUDs and natural family planning. These options do not increase your risk of developing VTE.
What should women looking to start the Pill do?
The researchers of the most recent British Medical Journal study recommend women starting the Pill are prescribed oral contraceptives with the lowest risk of VTE. That is, an older generation pill containing the progestogen levonorgestrel. The other advantage of these oral contraceptives is that they are listed on the PBS and so are less expensive.
It is also important for women to discuss possible side effects of the Pill with their doctor. Women who smoke, have high blood pressure or cholesterol, are obese, have a personal/family history of clotting disorders, or who suffer from migraine or heart disease have an increased risk of developing VTE. The risk of clotting also increases with age and prolonged immobilisation. Women most at risk are those who smoke, are aged 35 or older, and/or are relatively immobile.
When choosing the most suitable contraceptive method women should consider what their needs are (effectiveness, side effects, protection against sexually transmissible infections, etc.) and find out about possible risks.
Last Updated: December 2014
©Women's Health Queensland Wide Inc. This article was written by Joanna Egan and reviewed by the Women's Health Queensland Wide editorial committee. It was published in Health Journey 2013 Issue 4.