Combined hormonal contraception and venous thromboembolism

Abstract

This review provides an update of knowledge regarding venous thromboembolism (VTE) and combined hormonal contraceptives (CHCs) in the light of new progestins and new administration routes for CHCs. Practical recommendations are also offered. The association between the use of combined oral contraceptives (COCs) and an increased risk of VTE has been known about for many years, it being related mainly to the dose of oestrogen; however, recent research has also shown the influence of the type of progestin. When compared to COCs containing levonorgestrel or norethisterone, those containing desogestrel or gestodene present a two-fold greater risk of VTE; for COCs containing cyproterone acetate, the risk is four-fold greater, while there are no or insufficient data for those containing norgestimate, chlormadinone acetate or drospirenone. With regard to the contraceptive patch, the available data suggest that the risk of VTE is similar to that observed with COCs. There are no data concerning vaginal rings. The greatest risk of COC-associated VTE occurs during the first year of use, thus suggesting the existence of a predisposing condition, such as being a carrier of a thrombogenic mutation with which the COCs would exert a synergistic effect. Routine screening for such conditions is not justified. Changes in haemostatic variables produced by COCs, for example, acquired resistance to protein C, could be linked to VTE, although it has yet to be demonstrated that such alterations are related to a clinical risk of VTE among COC users. At present there are no laboratory tests able to detect an increased risk of VTE in asymptomatic women. The key procedures in terms of ensuring the safe use of this contraceptive method are a full clinical, personal and family history, in order to evaluate risk factors for VTE and cardiovascular disease, along with the recording of blood pressure and body mass index prior to the prescription of COCs.