Cld mild preeclampsia cause brain aneurysm formation in someone with family history or does blood pressure have to remain high for a longer period of time?

Difficult question: There is a form of brain aneurysm that is caused by chronic hypertension. However, other aneurysms are congenital and can rupture during bouts of temporary hypertension. Generally pregnancy induced hypertension is not dangerous and is well tolerated. Mri can look for congenital forms of aneurysm, but careful blood pressure management is appropriate regardless.

Not cause - rupture.: Preeclampsia cannot cause brain aneurysms, but can certainly make them rupture and cause massive strokes. Berry aneurysms in the brain vessels pre-date the pregnancy, but when it is complicated by pree they can leak or rupture with catastrophic consequences. The longer the preeclamptic hypertension goes untreated, the higher the risk of stroke (hemorrhagic, massive, occasionally lethal).