The Marfan's syndrome is an autosomal dominant genetic disorder resulting in a diminished strength of connective tissue. The ocular, skeletal and cardiovascular systems are mostly at risk. Principal complications of the disease are aortic dilatation and the risk of acute dissection. Pregnancy increases this risk. Based on the experience of our obstetrics department and after reviewing medical literature, we have tried to establish guidelines for obstetric care adapted to pregnant patients affected by Marfan's syndrome. Women with aortic root > 40 mm should avoid pregnancy. In all cases B-adrenergic receptor blockers must be used as soon as possible. Because there is a 50% risk that offspring will inherit the syndrome, prenatal diagnosis should be suggested. In addition to usual pregnancy monitoring, echocardiography should be performed every 3 months as well as 2 months after delivery. No increase of obstetrical complications has been shown in these patients. Route of delivery also depends on the diameter of the aortic root: vaginal delivery is warranted if the aortic root is<40; cesarean section should be performed in the other cases. Thus, with appropriate supervision, women with Marfan's syndrome will tolerate pregnancy without any adverse effect.