Pregnancy and Risk of Intracerebral Hemorrhage

Abstract

Pregnancy is a known risk factor for stroke, and hemorrhagic stroke accounts for approximately 60% of all strokes arising in pregnancy and up to the conventional 6-week postpartum period. 1 Meeks et al 2 completed a US population-based cohort study including 3 314 945 pregnant women. They chose to extend the postpartum period to 24 weeks after birth and used a cohort-crossover study design to minimize cofounding. With the cohort-crossover design, a pregnant or postpartum woman was compared with her future nonpregnant self. Specifically, the pregnancy period of assessment for intracerebral hemorrhage (ICH) was from 40 weeks before the index birth up to 24 weeks thereafter (the cohort period), whereas the follow-up comparison (crossover) period started 52 weeks after the cohort period ended and continued for another 64 weeks thereafter. Sandwiched in between the cohort and crossover periods was a 52-week interim period, in which a death or subsequent pregnancy was excluded from the analyses. Clearly, a woman had to be alive at the end of the interim period, which may introduce survivor bias, in that ICH has a high case-fatality rate, 1 so a woman with a fatal ICH would be missed. Moreover, it was assumed that each pregnancy ended at 40 weeks' gestation, which is certainly not the case in women who experience ICH in pregnancy, who

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