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 (BAVMs) is higher during pregnancy, delivery or puerperium. We compared occurrence of BAVM hemorrhage in women during this period with occurrence of hemorrhage outside this period during their fertile years.
Methods – We included all women with ruptured BAVMs (16-41 years) from a retrospective database of patients with BAVMs 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 BAVM 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 BAVM rupture during pregnancy, delivery, or puerperium was 6.8 (95% confidence interval [CI] 3.6-13) according to the case-crossover method and 7.1 (95%CI 3.4-13) using the self-controlled case-series method. In Scottish women, the relative rate was 1.3 (95%CI 0.39-4.1) using the case-crossover method and 1.7 (95%CI 0.0-4.4) according to the self-controlled case-series method. Because of limited overlap of CIs we refrained from pooling the cohorts.
Conclusions – Case-crossover and self-controlled case series analyses reveal an increase in relative rate of brain AVM 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.