Fetal and Neonatal Cardiology
Fetal and transitional circulation
The fetal circulation uses three shunts: ductus venosus, foramen ovale, and ductus arteriosus. Oxygenated umbilical blood preferentially reaches the left atrium and brain, while the ductus arteriosus diverts blood away from the lungs. At birth, lung inflation lowers pulmonary vascular resistance, pulmonary blood flow rises, and the foramen ovale and ductus arteriosus close functionally. Prenatal diagnosis of congenital heart disease allows delivery planning, prostaglandin availability, and parental counseling. Fetal echocardiography is usually performed at 18–22 weeks for suspected structural disease or arrhythmia.
Traps
Fetal tricuspid regurgitation and a small pericardial effusion can be normal. Cardiomegaly in a fetus does not always mean structural heart disease; anemia, arrhythmia, and twin-twin transfusion are alternatives. A newborn with a ductal-dependent lesion may appear stable until the ductus closes. Do not rely on prenatal findings alone; confirm postnatally.
Worked example
A fetus has suspected hypoplastic left heart syndrome. Plan delivery at a center with pediatric cardiac intensive care and prostaglandin E1 available. After birth, maintain ductal patency and avoid supplemental oxygen that may accelerate ductal closure unless needed for pulmonary disease. Rule of thumb: when a lesion is ductal-dependent, the ductus is the lifeline-protect it.