GPs should reconsider the way in which they prescribe oral contraceptives to take further account of the risks of venous thrombosis, a study in the BMJ has concluded.
The authors of the Dutch study suggested that all contraceptive pills are ‘equally effective’ when it comes to pregnancy rates and that other factors, such as thrombosis risk, should act as a key deciding factor for women who wish to use the pill as their method of contraception.
The research found that using combined oral contraceptive pills increase the risk of venous thrombosis by ‘at least two-fold’, with some pills increasing the risk by as much as four-fold. The study also found that the risk for people using pills containing third generation progestogens was elevated compared with those using pills containing second generation progestogens.
Instead, the study recommended using pills containing 30 micrograms of ethinylestradiol with levonorgestrel.
Dr Olaf Dekkers, a research fellow at the Leiden University Medical Center in the Netherlands and one of the study’s authors, said: ‘You can see that risk is increased by all types of pills and the lowest has an increased risk of at least two-fold compared to non-use. I think that’s a robust and important message, especially if you keep in mind that one hundred million females are taking oral contraceptives.’
He added: ‘The GPs and the patients can now really look what the risks are for the individual pills compared to all other types of pills and I really think that can help them make an informed decision.’
However, according to Dr Sarah Jarvis, the RCGP’s women’s health lead and a GP in South West London, the study ‘doesn’t tell us anything new’ and confirms figures that have been around ‘for years.’
She added that the risks of venous thromboembolisms are made clear to patients and that all GPs should be using ‘contra-indications’ to determine if patients should be prescribed oral contraceptives.
Dr Jarvis said: ‘It confirms what we knew before. It’s quite interesting to have them all set up together but that’s about it. I think in real terms, would it modify my prescribing? No, because it’s all stuff that was already out there. What it does is confirms what we knew before which is that patients need to be aware of the risks and the benefits.’
The link between combined oral contraceptives and a higher risk of a clot in the leg or a venous thromoembolism than not taking any contraception at all is ‘in the British National Formulary and has been for years and the size of the risk is very similar to the figures that have been given for years by the BNF’, she said.
Dr Jarvis added: ‘We always look for instance at cautions of venous thromboembolisms. So if you like, one caution is a caution and we explain to patients that two cautions is a contra-indication so everybody should be doing that. So, for example, being over 35 is a caution and smoking is a caution, if you’re over 35 and you smoke, you don’t get the pill.’