Relative risk of hemorrhage during pregnancy in patients with brain arteriovenous malformations

Background It is unclear whether the risk of bleeding from brain arteriovenous malformations is higher during pregnancy, delivery, or puerperium. We compared occurrence of brain arteriovenous malformation hemorrhage in women during this period with occurrence of hemorrhage outside this period during their fertile years. Methods We included all women with ruptured brain arteriovenous malformations (16-41 years) from a retrospective database of patients with brain arteriovenous malformations in four Dutch university hospitals (n=95) and from the population-based Scottish Audit of Intracranial Vascular Malformations (n=44). We estimated the relative rate of brain arteriovenous malformation rupture (before any treatment) during exposed time (pregnancy, delivery, puerperium) versus non-exposed time during fertile years, using the case-crossover design as primary analysis, and the self-controlled case-series design as secondary analysis. Results In 17 of 95 Dutch women and in 3 of 44 Scottish women, hemorrhages occurred while pregnant; none occurred during delivery or puerperium. In Dutch women, the relative rate of brain arteriovenous malformation rupture during pregnancy, delivery, or puerperium was 6.8 (95% confidence interval 3.6-13) according to the case-crossover method and 7.1 (95% confidence interval 3.4-13) using the self-controlled case-series method. In Scottish women, the relative rate was 1.3 (95% confidence interval 0.39-4.1) using the case-crossover method and 1.7 (95% confidence interval 0.0-4.4) according to the self-controlled case-series method. Because of limited overlap of confidence intervals, we refrained from pooling the cohorts. Conclusions Case-crossover and self-controlled case series analyses reveal an increase in relative rate of brain arteriovenous malformation rupture during pregnancy in the Dutch cohort but not in the Scottish cohort. Since point estimates varied between both cohorts and numbers are relatively small, the clinical implications of our findings are uncertain.