Fetal Circulation

Fetal Circulation

1. Foramen Ovale

   • Normally closes at birth and forms the fossa ovalis (depression in RA)
     • Closes due to decreased pulmonary pressures and when the LA pressure exceed the RA pressure
   • In about 30% of adults they may still have a small PFO that hasn't closed completely at birth, this can increase risk of cerebrovascular events
   • Fetal cardiac shunt which allows blood to enter the LA from the RA
     • Allows blood to bypass the nonfunctional fetal lungs while the fetus obtains its oxygen from the placenta.
   • Develops in the late 4th of gestation

2. Ductus Arterosis

   • Connects the PA to the proximal descending aorta
     • Allows most of the blood from the RV to bypass the fetus's fluid filled non-functioning lungs
   • Upon closure at birth becomes ligamentum artiosum
     • Non functional and formed within three weeks of birth
       • Can play a role in major trauma as it fixes the aorta in place and during rapid recoil can result in a ruptured aorta
   • Patent ductus arteriosis
     • When the ductus arteriosis fails to close