A patient with the Marfan syndrome died suddenly from aortic rupture and dissection in the early puerperium of her second pregnancy. Although the association of the Marfan syndrome and pregnancy is extremely rare, the case reported here being only the fifth on record, the concurrence of dissecting aneurysm or aortic dissection with pregnancy is more frequent. Furthermore it is accepted that aortic dissection in young women below the age of 40 is more common in the pregnant than those not pregnant. The cause of the enhancing effect of pregnancy is unknown but is thought to be endocrine since the stability of connective tissue can be influenced by hormones, particularly the sex steroids. An unusual feature of the present case is the florid inflammatory reaction in the adventitia of the aorta, not specifically related to pregnancy or to the Marfan syndrome, and it is assumed that in this patient the congenital defect of connective tissue assumed to be the basis of the Marfan syndrome is associated with an acute collagen change or necrosis, possibly illustrating a link between the heritable disorders of connective tissue and the diffuse collagen disease.