Contraceptive pills that contain one of the newer types of progestogen hormone are associated with an approximately twofold higher risk of venous thromboembolism (VTE) than pills containing older progestogen, according to a study published online in BMJ.
The increased risk for VTE with combined oral contraceptives is well-known, but previous studies have used different methods that left the relative risks associated with different combinations inconclusive, said senior author Julia Hippisley-Cox, MD, and colleagues.
The group analyzed 10,562 cases of VTE and prescription data for women aged 15 years to 49 years from two large population databases. They found that women who used any combined oral contraceptives have an increased risk of VTE compared with those who did not.
Women using older pills that contain levonorgestrel and norethisterone had a risk of VTE that was approximately 2.5 times higher than for women not using oral contraceptives, whereas women using newer pills that contain drospirenone, desogestrel, gestodene, and cyproterone had a risk of VTE that was approximately four times higher.
The authors emphasized that the threefold increased risk of VTE reported in this study with oral contraceptives is still lower than the nearly 10-fold increased risk of VTE in pregnant women.