Perinatal Adaptation Flashcards
What are the functions of the placenta?
Foetal homeostasis Gas exchange Nutrition transport Waste product transport Acid-base balance Hormone production Transport of IgG
What does the placenta ultimately prepare the baby for?
Delivery
What are the three shunts present in the foetal circulation?
Ductus venosus, foramen ovale, ductus arteriosus
What should happen to all three shunts in the foetal circulation after the baby is born?
They should close
How much of the foetal output goes to the lungs?
Only 7%
What shunt does oxygenated blood pass through when it is passing from the liver to the heart?
Ductus venosus
What does the foramen ovale allow?
Allows blood to pass from the right ventricle to the left ventricle
Why does very little blood go to the right ventricle in the foetal circulation?
The lungs are not fully developed yet so blood is not oxygenated there
What shunt does blood pass through when going to the foetal lungs?
The ductus arteriosus
Why is the foetus in a more hypoxic state than the delivered baby?
Oxygenated and deoxygenated blood is mixed in the foetal circulation
How does the baby prepare for being born during the third trimester?
Produces surfactant
Accumulates subcutaneous fat, glycogen and brown fat
Swallowing amniotic fluid
Where does brown fat accumulate in a baby?
Between the scapulae and around the internal organs
What purpose does swallowing the amniotic fluid serve?
Helps to grow and expand the lungs
What occurs in the foetus during the onset of labour?
There are increased catecholamines and cortisol
When does synthesis of fluid stop in the foetus?
Once labour has commenced and the baby is being delivered
How does vaginal delivery help the lungs adapt?
Squeezes the lungs = gets rid of 30% of 100ml lung content
How does the baby get rid of 70% of the fluid in its lungs after it is born?
By crying
What does a baby do in the first seconds after it is born?
Baby is blue, starts to breathe, begins to cry, gradually turns pink, cord is cut (usually delayed for 1 min)
What happens to vascular resistance once the baby is born?
Pulmonary vascular resistance drops and systemic vascular resistance rises
What circulatory changes occur once a baby is born?
Circulating prostaglandins drop
Duct constricts and foramen ovale closes
What causes the foetal ducts to closes after birth?
pO2 increases
Flow and prostaglandins decrease
What happens to the foetal shunts after birth?
Foramen ovale = closes or persists (10%)
Ductus arteriosus = become ligamentum arteriosus (rarely persists)
Ductus venosus = becomes ligamentum teres
What can cause the failure of cardiopulmonary adaption?
Non-functioning placenta = alters acid-base balance
Prematurity
Sepsis
Prolonged hypoxic state
What is the underlying reason for persistent pulmonary hypertension of the newborn?
Failure of the cardiopulmonary adaption
Why can persistent pulmonary hypertension of the newborn be life-threatening?
Lungs are unable to inflate so have high pressure which prevents the oxygenation of blood
Why does mixing of deoxygenated and oxygenated blood occur in persistent pulmonary hypertension of the newborn?
Foetal shunts don’t close as systemic vascular pressure is lower than pulmonary vascular pressure
What is used to diagnose persistent pulmonary hypertension of the newborn?
Pre-imposed ductal saturation monitoring = difference of more than 3% is diagnostic
How is pre-imposed ductal saturation monitoring carried out?
Probe put on right hand (measures pre-ductal saturation) and another put on left foot (measures post-ductal saturation)
How is persistent pulmonary hypertension of the newborn treated?
Ventilation, oxygen, nitric oxide (must be careful not to over-correct), sedation, inotropes, ECLS
What are some features of transient tachypnoea?
Common, usually diagnosis of exclusion, resolves quickly, baby may grunt and usually gets infection screening
What causes transient tachypnoea?
Usually occurs in big healthy babies born by section = no vaginal squeeze to empty fluid from lungs
What are some factors that contribute to a baby’s ability to thermoregulate?
Large surface area = babies proportionally have large head
Wet when born
Unable to shiver
Peripheral vasoconstriction
What are the four ways heat can be lost?
Evaporation, conduction, convection, radiation
What is the main way babies produce heat?
Non-shivering thermogenesis = heat produced by breakdown of brown fat in response to catecholamines
What is the main issue with using non-shivering thermogenesis as main way to produce heat?
Process isn’t effective in first 12hrs of life
What temperature should babies be kept between?
36.5-37.5 degrees
Why is hypothermia common in premature and small full term babies?
They have low stores of brown fat, little subcutaneous fat and a larger surface area:volume ratio
How may hypothermia be prevented?
Dry the baby, put on a hat, skin to skin contact (best option), blanket/clothes, heated mattress, incubator
What happens to the baby’s glucose homeostasis once it is born?
Interruption to glucose supply from placenta and very little oral intake of milk = drop in insulin and increase in glycogen
How do babies control their glucose homeostasis?
Mobilisation of hepatic glycogen stores for gluconeogenesis
Able to use ketones as brain fuel
How may hypoglycaemia arise in a baby?
Increased energy demands = unwell, hypothermia
Low glycogen stores = small baby, premature
Inappropriate insulin:glucagon ratio = maternal diabetes, hyperinsulinaemia (usually transient)
Some drugs = beta blockers
What is the aim of the UNICEF Baby Friendly Initiative?
Help promote and support breastfeeding
What occurs during breastfeeding?
Baby starts to suckle = rooting and suck reflex
Feedback loop causes increase in supply
Composition changes = colostrum, foremilk, hindmilk
What are some benefits of breastfeeding?
Prevents cancer and post-natal depression
Cheaper and easier than bottle feeding
Helps with bonding
How much weight are babies expected to lose after their are born?
About 10% of their birth weight
Why does foetal haemoglobin become disadvantageous?
Has high affinity for oxygen but doesn’t release it easily to tissues
What shifts the oxygen dissociation curve to the right in babies once they are born?
Increase in 2,3 BPG
What impact does the slower synthesis of adult haemoglobin have?
Causes physiological anaemia in babies between 8-10 weeks (reticulocyte count should be checked to ensure this isn’t any underlying pathology)
Where does haematopoiesis move to once the baby is born?
From the liver to the bone marrow
What causes physiological jaundice in babies?
Liver enzymes present but immature = only harmful if high levels of unconjugated bilirubin
How does jaundice arise in babies?
Foetal haemoglobin is broken down but conjugation pathways are immature = rise in unconjugated bilirubin
When may jaundice in babies be pathological?
If it is prolonged or has an early onset
How is jaundice treated in babies?
Phototherapy or exchange transfusion (only if severe)
Why is unconjugated bilirubin harmful in babies?
May cross BBB and settle in basal ganglia = causes cerebral palsy in later life
How is phototherapy used to treat jaundice in babies
Blue light used to change unconjugated bilirubin to excretable form and babies then pee it out
What are the risk factors for adaption problems in a foetus?
Hypoxia or asphyxia during delivery Very small/large babies Prematurity Maternal illness or medications Ill babies (sepsis, congenital abnormalities)
