Single Best Answer (SBA) · Abnormal Transition at Birth

A clinician explains the stimuli that close the ductus arteriosus after birth. Which single combination is correct?

Choose one answer.

Show answer and explanation

Answer: A. Increased oxygen tension and reduced prostaglandin E

The ductus arteriosus connects the pulmonary artery to the descending aorta in the fetus.

After birth, the increase in systemic vascular resistance causes the flow in the ductus to reverse.
Increased oxygen tension and reduced prostaglandin E production stimulate ductal constriction.
In most neonates, the ductus arteriosus is functionally closed by about 24 hours.

Event at birth	Consequence
First breath (negative pressure, ~80 ml air)	Lungs expand; functional residual capacity established
Lung expansion + raised alveolar oxygen	Pulmonary vascular resistance falls; blood flows to the lungs
Cord clamped (placenta removed)	Systemic vascular resistance rises
Ductus arteriosus	Flow reverses; oxygen and reduced prostaglandin E close it (usually by 24 hours)
Foramen ovale	Rising left atrial pressure (above right) closes it

In some conditions, prostaglandins are used to keep the duct open (duct-dependent congenital heart disease), and prostaglandin inhibitors can help close a persistent duct.

So oxygen and falling prostaglandin E close the ductus arteriosus.

More on Abnormal Transition at Birth