fetal circulation

structures of fetal circulation:

• umbilical vein- carry oxginated blood from placenta to fetus

• ductus venosus- connect umbilical vein to inferior vena cava to right side of heart

• foramen ovale- allow blood flow directly from right to left atrium

• ductus arteriosus- connect pulminary arteral trunk to aortic arch and bypass the lungs

• umbilical arteries- return blood to placenta from internal iliac arteries

fetal circulation:

• blood leave placenta through umbilical vein

• 50% bypass liver- ductus venosus

• joins inferior vena cave and enter right atrium

• most pass to left atrium through foramen ovale

• pumped into left ventricle then ascending aorta to brain trunk

• small amount from right atrium via tricuspid valve to right ventricle

• 10% via pulminary artery trunk to lungs

• 90% through ductus arteriosus then descending artery to limbs

• from descending aorta to hypogastric atreries to internal iliac arteries

• return to placenta- umbilical arteries

fetal heart:

changes at birth:

• changes from fetal- adult type circulation (happen in 60 secs)

• no longer dependant on mother for gass exchange- own lungs

• clamping of cord/ first breath- cause change in cardiovascular system

• all arteries and veins in umbilical cord close and constrict

events that can cause hypoxia in baby:

• apnoea

• bradycardia

• hypoglycaemia

• uncontrolled seizures

• inc pulmonary vascular resistance w right to left shunting

• respiratory distress

midwife role:

• ensure airway clear

• dry baby- prevent heat loss/ hypothermia

• stimulate baby- rub

• delay cord clamping

• ensure baby gasp for air when cry