The ductus arteriosus in the premature baby
In premature babies however, the process by which the duct closes off sometimes does not function effectively. The bypass can remain open after birth which means that some of the blood will continue to flow through the duct. This condition is referred to as a ‘patent’ (meaning open) ductus arteriosus (PDA).

The more premature the baby is, the higher the risk of a PDA occurring.

What are the consequences of a PDA?
If the duct remains open after birth, the blood will flow from the aorta (7) to the pulmonary artery (3).

This may give rise to two situations:
1. Blood is ‘stolen’ from the aorta – which means that circulation to the body’s other organs is affected negatively.
2. The lungs will have blood flowing from the pulmonary artery and ‘extra’ blood from the aorta – so that the flow to the lungs will be too great.

How do you know if a baby has a PDA?
The most common symptom is some kind of respiratory (breathing) difficulty. Because the lungs are getting too much blood, the blood may ‘stagnate’ in the lungs. This can lead to problems of varying degrees of seriousness – ranging from slightly laboured breathing to major problems that require a ventilator to help the baby breathe.

However, it is not always so obvious that the duct has remained open. This applies particularly to babies that have lung problems with other causes after having been born prematurely.

How is the condition diagnosed?
Doctors may suspect a PDA if they hear a heart murmur or feel a very strong pulse. To confirm the diagnosis however, the baby’s heart and its circulation of blood must be examined using ultrasound.