This book opens with a review of the most common forms of congenital heart disease in pregnancy, outlines preconception counseling, discusses the associated morbidity and mortality of each lesion, and reviews current recommendations for the management of congenital heart disease in pregnancy. Women with congenital heart disease represent over 50% of patients with cardiac disease in pregnancy today. Formerly characterized by high rates of maternal morbidity and mortality, the authors explore how advancements in medical management and surgical intervention are responsible for increasing numbers of women with congenital heart defects experiencing safe and successful pregnancies. Additionally, the authors discuss cardiac resynchronization therapy in adults with congenital heart disease. This compilation goes on to discuss the four different types of atrial septal defects, categorized based on location and embryological development. The concluding study reviews the effects of high altitude effects on congenital heart disease in the Andean region, and in Ecuador as a study case. High-altitude hypoxia presents numerous challenges to human health, survival, and reproduction because of decreased oxygen availability brought on by lowered barometric pressure at high elevations.