Adaptation at Birth Flashcards
what are the functions of the placenta
fetal homeostasis gas exchange nutrient transport to fetus waste product transport from fetus acid base balance hormone production transport of IgG
what does the fetal liver do
produces albumin, clotting factors and RBCs
what does the fetal kidney do
excretes urine, contributes to amniotic fluid
describe the fetal circulations
The oxygenated blood is carried from the placenta to the fetus via the umbilical vein. About half of this blood passes through the hepatic capillaries and the rest flows through the ductus venosus into the inferior vena cava. Blood from the vena cava is mostly deflected through the foramen ovale into the left atrium, then to the left ventricle, into the ascending and descending aorta to supply to the fetus
goes back to placenta via the pulmonary arteries (branches of descending aorta)
Deoxygenated blood from the superior vena cava flows into the right atrium, right ventricle, and then into the pulmonary artery. Because of high pulmonary vascular resistance, only about 5 to 10 per cent of the blood in the pulmonary artery flows to the lungs, the majority of it being shunted through the patent ductus arteriosus and then down the descending aorta
name the three shunts in the fetal circulation and what they allow
ductus venosus (allows umbilical vein to pass through liver) foramen ovale (right to left shunt in heart, reduced blood going to lungs) ductus arteriosus (reduces blood going to lungs, mean oxygenated and deoxygenated blood mix in descending aorta)
what does the fetus do in the 3rd trimester to prepare for birth
produce surfactant
accumulation of glycogen - liver, muscle, heart (to prepare for starvation state)
accumulation of brown fat- between scapular and around internal organs (insulating fat)
accumulation of subcutaneous fat
swallowing amniotic fluid and ‘practise breathing’
where is surfactant produced
type 2 pneumocytes in alveoli
what is the role of surfactant
needed for gas exchange
reduces surface tension of alveoli allowing them to expand
what adaptations happen to the fetus during labour
increased catecholamine and cortisol at the onset of labour
synthesis of lung fluid stop
during vaginal delivery lung fluid gets squeezed out
first cry helps absorb left over fluid into lymphatic system
what colour do babies come out
blue/ pale
gradually goes pink after starts to breath/ cry
why is delayed cord clamping important
allows blood volume and immunoglobulin transfer to baby, helps prevent amaemia
what happens to the circulation after birth
pulmonary vascular resistance drops (onset of breathing expands and aerates the lungs)
systemic vascular resistance rises (cord clamped, placenta =low resistance vascular bed removed)
oxygen tension rises (pO2 rises from 2-3.5 kPa to 9-13kPa)
duct (venosus and arteriosus) constricts
foramen ovale closes
what is the fetal level of oxygen (pO2)
2-3.5 kPa
what causes duct constriction in fetal adaptation
increased pO2 (muscle layer is oxygen sensitive)
decreased flow of blood
decreased prostaglandins
when does the ductus close
physiological closure within first few hours/ days
anatomical closure within 7-10 days
what happens to the foramen ovale
closes or persists as PFO (10%)
what happens to the ductus arteriosus
becomes ligamentum arteriosus or persists as duct
what happens to the ductus venosus
becomes ligamentum teres
what can cause failure of cardiorespiratory adaptation
asphyxia (causing hypoxia/ acidosis) prematurity sepsis hypoxia (meconium aspiration) cold stress
what is persistent pulmonary hypertension of the newborn
when lung vascular resistance fails to fall meaning the shunts stay open (right to left flow at PFO and PDA)
Any oxygenated blood comes back into La however PFO and PDA means the oxygenated blood mix with deoxygenated meaning majority of circulation will be deoxygenated blood
