A new study published online in the journal Contraception examines whether the risk of venous thromboembolism (VTE) and arterial thromboembolism (ATE) is increased in women using non-oral combined hormonal contraceptives compared to women using combined oral contraceptives (COC).

Researchers from the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) explored the PubMed database and extracted articles for analysis through May 2016 from database inception. They specifically included primary research studies that examined women using the patch, ring, or combined injectables compared with women using levonorgestrel-containing or norgestimate-containing COCs. Their search identified a total of 8 studies. 

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Analyses found that from 6 studies assessing VTE among patch users and levonorgestrel or nongestimate-containing COC users, two of the studies showed a statistically significant elevated risk of VTE for patch users (risk estimates 2.2–2.3),however four studies showed no increased risk. Of three studies examining VTE among ring users compared with levonorgestrel COC users, one found a statistically significantly elevated risk among patch users (risk estimate 1.9), however two studies did not.

Two studies investigating ATE among women wearing a patch compared to those using norgestimate COCs found no increased risk.

Overall, the authors assert that their meta-analyses had found ‘Limited level II-2 good to fair evidence’ of conflicting results on the existence of a higher risk of VTE for women wearing a patch or ring compared to those using COCs. They concluded that, ‘additional studies with standard methodology are needed to further clarify any associations and better understand mechanisms of hormone-induced thrombosis among users of non-oral combined hormonal contraception.”

For more information visit ContraceptionJournal.org.