Reported in the paper are three cases of women at reproductive age presenting with Marfan's syndrome. They all underwent urgent surgery because of a threat of rupture of dissecting aneurysm during pregnancy (n = 1). All experienced uneventful recovery. Recommendations are giver as to observation over such patients. The author has reached the conclusion that in case of impending or already developed dissection it is necessary that cesarean section be done on an urgent basis to save life of the mother and fetus alike, with surgical correction of aortic aneurysm and of aortic incompetence being indicated following the cesarean operation.