Fetal circulation and perinatal programming

In fetal life, the systemic and pulmonary circulations exist in parallel, rather than in series, permitting survival even in the presence of complex congenital heart disease. The fetal heart also differs in terms of its structure and function and has a limited ability to modify cardiac output. Increases in afterload are associated with marked depression in cardiac function. Much has been learnt from fetal cardiac imaging, not only for detection but also for understanding of pathophysiology and transition to the postnatal circulation.