INTRODUCTION: Currently available combined oral contraceptives (COC) reportedly increase the risk of venous thromboembolism (VTE). We aimed to quantify this risk considering both progestogen type and estrogen dose.
MATERIALS AND METHODS: PubMed, Embase and LIVIVO were searched for relevant publications until April 2017. Case-control and cohort studies including healthy women taking COC and assessing incident VTE as outcome were selected. Adjusted relative risks (RR) with 95% confidence intervals (CI) derived from random effects model using a generic inverse-variance approach are reported.
RESULTS: Overall, 1,359 references were identified and 17 studies were included in the meta-analysis. The pooled RR of VTE was associated with various COC, with the association depending on their respective estrogen dose and progestogen type. Compared to the reference, levonorgestrel with 30-40?µg ethinylestradiol, the overall risk of VTE was higher for all other COC. Preparations with desogestrel with 30-40?µg estrogen showed the highest relative risk (RR: 1.46; 95% CI: 1.33-1.59), while RRs for drospirenone (30-40?µg ethinylestradiol) and desogestrel (30-40/20?µg ethinylestradiol) were lower. COC containing gestodene and cyproterone with 30-40?µg estrogen showed the lowest risk (RR: 1.27; 95% CI: 1.15-1.41 and RR: 1.29; 95% CI: 1.12-1.49, respectively).
CONCLUSIONS: Compared to levonorgestrel with 30-40?µg ethinylestradiol, all COC showed a significantly increased VTE risk. The association varied depending on the progestogen type and the dose of estrogen. Our results suggest that the prescription of COC with the lowest possible dose of ethinylestradiol may help to avoid VTE cases among young, healthy women.
Interesting systematic review and meta-analysis trying to clarify the different risk of VTE associated with different combined oral contraceptives. However, there is another systematic review published on Int J Gynaecol Obstet. 2018 on the same topic, which is more clearly reported.
As is well known and as the authors themselves acknowledge, the quality of a meta-analysis strongly depends on the quality of the studies included. As such, the importance of this analysis is questionable, even though the concern (VTE risk with the different oral contraceptive drugs) is a legitimate (and persistent) one.