The risk of aneurysmal subarachnoid hemorrhage during pregnancy, delivery, and the puerperium in the Utrecht population: case-crossover study and standardized incidence ratio estimation.

BACKGROUND AND PURPOSE It is unclear whether the risk of aneurysmal subarachnoid hemorrhage (aSAH) is increased during pregnancy, labor, and the puerperium. We compared the risk of aSAH during this period with the risk outside this period. METHODS We included women with aSAH between 18 and 42 years of age (n=244) from our prospectively collected database of patients with subarachnoid hemorrhage treated in the University Medical Center Utrecht, the provincial referral center, between January 1987 and April 2006. We estimated the relative risk of aSAH during pregnancy, delivery, or the puerperium by a case-crossover design and calculated a standardized incidence ratio, dividing the observed number of patients with aSAH during pregnancy, delivery, or puerperium by the expected number based on the incidence in the general population of women of the same age during the study period. RESULTS Of the 244 women, 4 were pregnant, 3 in the puerperium and none in labor. The relative risk of aSAH during pregnancy, delivery, or the puerperium was 0.4 (95% CI, 0.2 to 0.9). Based on the number of women aged 18 to 42 years within the catchment area of our hospital and the number of pregnancies within the study period, the expected number of patients with aSAH during pregnancy, delivery, or the puerperium was 12, resulting in a standardized incidence ratio of 0.6 (95% CI, 0.2 to 1.1). CONCLUSIONS The risk of aSAH is not increased during pregnancy, labor, and the puerperium. There is no need to advise against pregnancy in women with an increased risk of subarachnoid hemorrhage and no evidence to advise against vaginal delivery in such women.