Background Prior studies on rupture risk of brain arteriovenous malformations (AVMs) in women undergoing pregnancy and delivery have reported conflicting findings, but also have not accounted for AVM morphology and heterogeneity. Here, we assess the association between pregnancy and the risk of intracranial hemorrhage (ICH) in women with AVMs using a cohort-crossover design in which each woman serves as her own control.

Methods Women who underwent pregnancy and delivery were identified using DRG codes from the Healthcare Cost and Utilization Project State Inpatient Databases for California (2005–2011), Florida (2005–2014), and New York (2005–2014). The presence of AVM and ICH was determined using ICD 9 codes. Pregnancy was defined as the 40 weeks prior to delivery, and postpartum as 12 weeks after. We defined a non-exposure control period as a 52-week period prior to pregnancy. The relative risks of ICH during pregnancy were compared against the non-exposure period using conditional Poisson regression.

Results Among 4 022 811 women identified with an eligible delivery hospitalization (median age, 28 years; 7.3% with gestational diabetes; 4.5% with preeclampsia/eclampsia), 568 (0.014%) had an AVM. The rates of ICH during pregnancy and puerperium were 6355.4 (95% CI 4279.4 to 8431.5) and 14.4 (95% CI 13.3 to 15.6) per 100 000 person-years for women with and without AVM, respectively. In cohort-crossover analysis, in women with AVMs the risk of ICH increased 3.27-fold (RR, 95% CI 1.67 to 6.43) during pregnancy and puerperium compared with a non-pregnant period.

Conclusions Among women with AVM, pregnancy and puerperium were associated with a greater than 3-fold risk of ICH.