P29.3: Persistent fetal circulation

After the birth, the blood circulation system has not adapted in the usual way.

Blood supplies oxygen and nutrients to the tissue in the body. The child's blood circulation system is different during its time in the womb to after the birth.

After the birth, the heart pumps the blood through certain blood vessels to the lungs. These blood vessels are called the pulmonary arteries. In the lungs, the blood is enriched with oxygen from inhaled air. The blood then flows back to the heart, and from there it flows to the body via the aorta.

While the child is in the womb it is not breathing. So the child's blood cannot be enriched with oxygen via the lungs. Instead, the child receives oxygen from the mother's blood via the umbilical cord. So there are special connections in the blood circulation system. For example, there is a connection, through which the blood flows, between the two halves of the heart. There is also the connection between pulmonary artery and aorta. The child's blood then mostly flows past the lungs straight to the aorta.

The connections usually close immediately after the birth, when the child begins to breathe and the umbilical cord is cut. The blood circulation system adapts as a result. However, the connections may not close up after the birth.

For example, if the connection between the pulmonary artery and aorta does not close up, then blood continues to flow through this connection after birth. In this case, however, blood flows in the opposite direction from the aorta into the pulmonary artery. This creates additional blood flow between the heart and the lungs. This means that the heart and lungs are under greater strain. And the body may then not be adequately supplied with oxygen.

The baby may then have a variety of indications. Breathing may seem forced, or a moaning may be heard when breathing. Its skin may turn blueish and it may be short of breath. The child may also fail to grow properly and it may be weak.