The Fetal Circulatory System Simplified

In a standard circulatory system, the heart performs two functions, the right side pushes blood that comes from the body out to the lungs to get oxygen added to it.  The left side receives blood with oxygen from the lungs and pushes it out to the body.  This cycle repeats with every heart beat.

However, when you are carrying your baby inside you, you provide all the oxygen.  Because your baby isn't using the lungs for oxygen, there are two special connections that the body uses to make those two separate systems in to one big system.  The special connections are called Ductus Arteriosus and Foramen Ovale.



Typically, at birth, once oxygen hits the lungs those connections begin to close and over the course of the first 1-3 days they shut down converting the circulatory system over to the 2 step system I talked about above.

For most children, this shut down is important to proper heart function.  When those changes don't occur, there can be issues.  Children who don't have those connections close are diagnosed with a Patent Ductus Arteriosus, Patent Forman Ovale or both.  These can be closed surgically if they cause issues.

In the case of a number of critically complex congenital heart defects (CCHD), the closing of those special connections begins a crisis that must be quickly addressed.  In the cases where the extra connections are what is keeping the child alive, medicine called prostaglandin can be administered to keep those pathways open.

This is why a newborn pulseox screening is so critically important.  The test should occur after the baby is 24 hours old.  If a problem is detected, doctors can order further testing to determine the cause of low oxygen readings and administer the appropriate treatments.