Progestogen type impacts VTE risk associated with contraceptive pills
MedWire News: Women taking contraceptive pills containing one of the newer types of progestogen hormone, namely drospirenone, desogestrel, or gestodene, have twice the risk for venous thromboembolism (VTE) as those on pills containing the older progestogen levonorgestrel, research shows.
Several studies have investigated the relationship between combined oral contraceptives and VTE, and more recent data suggest that the risk may differ according to progestogen type, explain Øjvind Lidegaard (University of Copenhagen, Denmark) and colleagues.
In light of these reports, Lidegaard and team revisited the Danish registry data they had used in an earlier study, which assessed VTE risk in Danish women using hormonal contraception.
In the present study, the researchers assessed the risk for VTE from use of combined oral contraceptives according to progestogen type using data for nearly 1.3 million women aged 15-49 years between 2001 and 2009.
During 8,010,290 women years of observation, 4246 first ever VTE events were recorded, of which 2847 (67%) were confirmed (defined as women who were given anticoagulation therapy for at least four weeks).
Compared with nonusers of hormonal contraception, the relative risks for confirmed VTE in users of oral contraceptives containing 30-40 µg ethinylestradiol with levonorgestrel, desogestrel, gestodene, or drospirenone were 2.9, 6.6, 6.2, and 6.4, respectively.
Calculating rate ratios showed that oral contraceptives containing desogestrel, gestodene, or drospirenone conferred at least twice the risk for VTE as oral contraceptives with levonorgestrel. More specifically, compared with levonorgestrel the rate ratio for VTE was 2.2, 2.1, and 2.1 with desogestrel, gestodene, and drospirenone, respectively, after adjusting for length of use.
"If oral contraceptives with desogestrel, gestodene, or drospirenone are anticipated to increase the risk of VTE sixfold and those with levonorgestrel threefold, and the absolute risk of VTE in current users of the former group is on average 10 per 10,000 women years, then 2000 women would need to shift from using oral contraceptives with desogestrel, gestodene, or drospirenone to those with levonorgestrel to prevent one event of venous thromboembolism in one year," Lidegaard and et al write in the BMJ.
In an accompanying editorial, Philip Hannaford from the University of Aberdeen, UK says "it is difficult not to conclude that combined oral contraceptives with desogestrel, gestodene or drospirenone confer a higher risk of venous thromboembolism than those with levonorgestrel" and that "many clinicians will choose to minimize the risk by prescribing a combined oral contraceptive with levonorgestrel whenever possible."
Hannaford stresses however that it is crucial "not to exaggerate the risk - oral contraceptives are remarkably safe and may confer important long term benefits in relations to cancer and mortality."
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By Laura Dean