Association Between Pregnancy and Symptomatic Hemorrhage in Women With Brainstem Cavernous Malformations and Bleeding in the Preceding Year: A Prospective Multicenter Study

Background The association between pregnancy and the risk of symptomatic hemorrhage (SH) in brainstem cavernous malformations remains uncertain. We aimed to quantify the risk of pregnancy‐associated SH in women with brainstem cavernous malformations. Methods We analyzed women with brainstem cavernous malformations in a prospective registry (2016–2022) experiencing pregnancy after enrollment. Follow‐up was divided into pregnancy‐associated segments (pregnancy plus ≤6 weeks postpartum or postabortion) and nonpregnant segments. Primary analysis used case‐crossover models; propensity score‐matched analyses assessed robustness. Results Among 63 women (median age, 30.0 years), 53 (84.1%) had bled before enrollment, including 45 (71.4%) with SH in the preceding year. Prospectively, they contributed 72 pregnancies and 371.7 patient‐years, observing 34 SHs. The pregnancy annual SH rate was 20.4% versus 7.2% nonpregnant (adjusted incidence rate ratio: 2.56, 95% CI, 1.11–5.93; P =0.028). Trimester‐specific and postpartum annual SH rates were 5.9%, 16.8%, 34.6%, and 38.3%; risk significantly increased only during the third trimester ( P =0.004) and postpartum ( P =0.007). This pregnancy effect was confined to segments with SH in the preceding year (annual SH rates 46.7% versus 9.4%; P =0.007), which was an independent risk factor. Propensity score‐matched analyses yielded consistent results. Conclusions Pregnancy is associated with an elevated SH risk in women with brainstem cavernous malformations, specifically among those with SH in the preceding year. Because of selection bias, generalizability to asymptomatic or incidental lesions is limited, warranting cautious extrapolation. Registration URL: www.chictr.org.cn ; Unique Identifier: ChiCTR‐POC‐17011575.