This is the second edition of this guideline. The first edition was published under the same title in 2004.
Purpose and Scope
The Venous thromboembolism (VTE) includes deep vein thrombosis (DVT), pulmonary embolism and cerebral venous sinus thrombosis. Most data in relation to venous thrombosis and hormonal contraceptive use relates to DVT and pulmonary embolism. The true background incidence of VTE in women of reproductive age is often difficult to quantify but recent data suggest that the incidence has been underestimated and that it is more likely to be in the range of 50–100/100 000 woman-years. This is ten-fold higher than the widely quoted absolute risks for women of reproductive age who are not using contraception (5/100 000 womanyears). This increased incidence of VTE may in part be a result of improved study design, clearer diagnosis and definition of VTE. Despite this increase in background risk of VTE for women of reproductive age the absolute risk is still small.
There is synergism between genetic factors associated with venous thrombosis (such as factor V Leiden mutation, prothrombin 20210A, protein C or protein S deficiency, antithrombin III deficiency) and acquired risk factors (such as antiphospholipid syndrome, pregnancy, contraceptive use, surgery, trauma, immobilisation and malignancy). This guidance covers the VTE risk with hormonal contraception and the risk factors which are relevant when considering contraceptive choices and medical eligibility for contraceptive use. Categories for the safe use of hormonal contraception have been recently updated in the UK Medical Eligibility Criteria (UKMEC). In particular, categories relating to hormonal contraceptive use by obese women, women with systemic lupus erythematosus and antiphospholipid syndrome and current VTE are relevant for this guideline.
Non-randomised studies suggest an increased risk of VTE with combined hormonal (estrogen and progestogen) contraceptive use but confounding and bias cannot be excluded. The consistency of finding an increased risk among combined oral contraceptive users in most of the 20 or more studies examining the risk of VTE, compared with non-users, strongly suggests that the effect is real. There are fewer data on VTE risk with progestogen-only contraception and, although a lack of evidence does not necessarily suggest an absence of effect, it is generally accepted that progestogen-only methods of contraception are not associated with an increased risk of VTE.
Clinicians counselling women on hormonal contraceptive use should be able to convey the risk of VTE. Using appropriate language and written materials and providing a comparison of the risks and benefits may help women judge the level of risk that is acceptable to her. Although the relative risks of VTE do increase with combined hormonal contraceptive use, the absolute risk in women of reproductive age is very low.
This guldeline can be downloaded as a pdf using the link below.
