Managing High Risk Pregnancy in Single Ventricle Physiology with Acquired von Willebrand Disease: A Case Report

<b>Background and Clinical Significance:</b> Left ventricular hypoplasia is often repaired surgically in sequence to a Fontan circulation, which is a physiologic state that presents unique challenges during pregnancy. Although women with Fontan physiology can achieve successful pregnancy outcomes, they remain at elevated risk for cardiac, thrombotic, and obstetric complications. <b>Case Presentation:</b> We describe a 38-year-old woman with Fontan physiology and acquired von Willebrand syndrome (AVWS) who was admitted at 23 weeks gestation for preterm premature rupture of membranes. The patient had history of prior classical cesarean delivery and two previous miscarriages. Her pregnancy was further complicated by abnormal placental vasculature and uterine arteriovenous malformation. Given her bleeding diathesis, hematology advised against anticoagulation or antiplatelet therapy, and she ultimately underwent a successful low transverse cesarean delivery under general anesthesia at 24 weeks. Postpartum hemorrhage was managed with clotting factor replacement and supportive care. <b>Conclusions:</b> This case illustrates how AVWS may mitigate thrombotic risk in Fontan physiology and how early activation of a cardio-obstetrics team can enable tailored planning. As more patients with complex congenital heart disease reach reproductive age, multidisciplinary coordination, shared infrastructure, and individualized birth plans will be essential to achieving optimal maternal-fetal outcomes.