The risk of venous thrombosis, including cerebral vein thrombosis, among women with thrombophilia and oral contraceptive use: a meta-analysis.

Several small studies have reported an elevated risk of venous thrombosis (VT) with thrombophilia and oral contraceptive (OCP) use. We aimed to summarize the risk of VT among women with thrombophilia and OCP use and to assess the interaction between the 2 factors. We selected 15 studies that assessed the prevalence of OCP use and thrombophilia among reproductive-aged women. Odds ratios (ORs) were calculated for each study and pooled using the random effects model. We found an increased risk of VT among women with OCP use (pooled OR 3.0, 95% confidence interval [CI] 1.9-4.5) and with thrombophilia (pooled OR 4.5, CI 3.4-5.9), respectively. Heterogeneity was significant (I (2) >80%). Women with both thrombophilia and OCP use had a 14-fold risk of VT compared to healthy OCP nonusers (pooled OR 14.25, CI 6.2-32.8). Oral contraceptive use and thrombophilia similarly increase VT risk. Our study confirms an interaction between OCP use and thrombophilia.