There are no prospective studies of pregnancies for the diseases studied here in (Heredity Hemorrhagic Telangiectasia, Marfan syndrome or related, primary lower limb lymphedema, superficial arteriovenous malformations, and cerebro-spinal arteriovenous malformations) although complications of these can present life-threatening health problems for the mother and her baby. The purpose of this National prospective study is to obtain greater insight into obstetrical complications associated with rare maternal vascular genetic disorders in order to improve prevention and to reduce risk of death. In this context, experts and patient associations consider that there is a need to make real progress in the formulation of recommendations based on scientific data.