Neonatal Nurse Practitioner Practice Exam

What is considered the primary mechanism for closure of the ductus arteriosus after birth?

1. Increased blood flow from the aorta

2. Decreased prostaglandin E levels

3. Increased pulmonary blood flow

4. Increased venous return

The correct answer is: Decreased prostaglandin E levels

The primary mechanism for the closure of the ductus arteriosus after birth is the decreased levels of prostaglandin E. During fetal life, the ductus arteriosus is kept open (patent) by the presence of prostaglandins, which are produced by the placenta and are essential for maintaining fetal circulation. After birth, when the placenta is removed, there is a significant reduction in prostaglandin E levels in the newborn circulation. This decrease leads to the constriction of smooth muscle within the ductus arteriosus, resulting in its closure. Additionally, the establishment of normal pulmonary circulation and the increased oxygenation, along with the increased blood flow from the aorta, contribute to the physiological changes required for the ductus arteriosus to close. However, the roles of increased pulmonary blood flow and increased venous return are secondary mechanisms that occur after the primary action of reduced prostaglandin E has taken place. Therefore, the decrease in prostaglandin E levels is the most immediate and direct cause for the functional closure of the ductus arteriosus.