"Hormonal contraception and venous thrombosis."

Background. New studies about the influence of hormonal contraception (HC) on the risk of venous thromboembolism (VTE) have been published. 

Material and methods. Studies assessing the risk of specific types of hormonal contraception were evaluated, compared and set into a clinical perspective. 

Results. The majority of newer studies have demonstrated a three fold increased risk of VTE in current users of middle- and low-dose combined oral contraceptives (COCs) with norethisterone, levonorgestrel or norgestimate compared with non-users. 

The same studies have demonstrated a six-fold increased risk of VTE in users of combined pills with desogestrel, gestodene, drospirenone or cyproteroneacetate, and in users of the contraceptive vaginal ring, compared with non-users. The rate ratio of VTE between COCs with newer progestogens as compared with users of COCs with levonorgestrel was 1.5-2.8 in seven and 1.0 in two studies. Progestogen-only contraception did not confer an increased risk of VTE in any study.

The incidence rate of VTE in non-pregnant non-HC using women 15-49 years is 4 per 10 000 years. 

Recommendations. For starters on hormonal contraception, we recommend middle or low-dose combined pills with norethisterone, levonorgestrel or norgestimate as 1(st) choice preparations. For the many women who are users of COCs with newer progestogens, although the absolute risk of VTE is low, a change to combined pills with norethisterone, levonorgestrel or norgestimate may half their risk of VTE. Finally, we recommend COCs with 20 μg estrogen combined with the older progestogens to be launched in the Scandinavian countries. Women at an increased risk of VTE should consider progestogen-only contraception or non-hormonal contraception.