Physiological adaptation from foetus to neonate Flashcards
describe the in utero environment
- Foetus surrounded by amniotic fluid
- Warm cushioned quiet
- Fluid filled lungs
- Foetal circulation
- Relative hypoxia – oxygen and carbon dioxide exchange via placenta
- Nutrient acquisition and waste elimination via placenta
what are the lungs like before brith
- Lungs are fluid filled – mediated by active chloride secretion
- Increasing secretion of surfactant with increasing gestation – starts at 24 weeks gestation, increased by glucocorticoids, cortisol and thyroid hormones
- The distending pressure of the fluid in the lung is important for lung exansopn and the development of the airways
what does the foetus make breathing efforts
- Foetus makes breathing efforts primarily during sleep
what happens to the foetus lungs at birth
- Physical pressure of labour squeezes some fluid out of the lung the rest goes into the lymphatic system
- Initial breath causes negative thoracic pressure – the hardest breath of your life, may cause small pneumothoraces from the initial breath
- Active absorption of alveolar fluid via sodium transport – stimulated by cortisol, catecholamines and thyroid hormone – switches from chloride to sodium absopriton
- Establishes a functional residual volume, onset of regular respriations
what can the first breath produce
small pneumothraces from the initial breath
what happens if you do not have surfactant
- get respiratory distress syndrome
- in order to treat them you have to give them surfactant and incubate them
- if you know they are gunna be born pre term then you give high doses of steroids to the mum as cortisol stimulate surfactant production
describe the cardiovascular system of the foetus
- placenta leads to umbilical vein which leads to the ductus venous which pumps the blood into the IVC
- the IVC goes to the right atrium
- it can then go to the right ventricle, into the pulmonary artery pulomyar vein and into the left atrium
- or it can go to the right ventricle pulmonary artery and ductus arteries into the aorta
- or it can go into the the foramen oval to the left atrium then left ventricle then aorta then internal lilacs and umbilical artery
where does most of the oxygenated blood supply go
supply the brain, and the coronary vessels from the heart
the diameter of the ductus arterioles can equal that of the …
aorta
what happens when the umbilical cord is clamped
- Umbilical cord is clamped
- And someone will cut it
- So the blood through the umbilical vessels are stop
- All that is left is the artery and body so the systemic vascular resistance rises
- The lungs have opened up the pulmonary blood flow has increased and pulmonary vascular resistance drops due to more oxygen, this reduces the blood pressure in the lungs
- RA pressure drops, LA pressure rises, reducing flow through foramen ovale
- Flow preferentially goes to RV and pulmonary artery
- Flow through ductus arteriosus changes
what can the umbilical arteries and veins be used for
- the umbiclia arteries can be used for quick access therefore they can give richly concentrated infusions via candlers
- umbilical arterial catheter - gives access to do blood tests and so you can work out the babies blood pressure
what happens in persistent pulmonary hypertension
- this is when the switch does not occur
- all the oxygenated blood is still pumping to the peripheral circulation
what happens once the foetus is born to the cardiovascular system
- ductus arteriosus clsoes
- foramen ovale closes
- umbilical vein forms the round ligament of the liver
- the umbilical arteries either becomes the medial umbilical ligament or the branch of the anterior division of the internal iliac artery
how does the ductus arterioles close
- Closure aided by increased oxygen and decreased prostaglandins (PGE2)
- Functionally closes within a few days
- Anatomically changes within a couple of weeks – forming ligamentum arteriosum
how does foramen oval close
Fuses in the majority but significant minority have a PFO – this usually doesn’t cause any problems but this can cause stroke in young people,
• Umbilical vein forms the round ligament of the liver
what happens to the umbilical artery after birth
- Partly obliterates and become the medial umbilical ligament
- Whereas A part remains open as a branch of the anterior division of the internal iliac artery.
when to foetal cortisol levels increase
Foetal cortisol levels increase during the third trimester and at birth
what does foetal cortisol levels do
- Stimulates surfactant production
- Activates thyroid hormone
- Matures hepatic glucose and gut digestive enzymes
- Increase in beta-adrenergic receptors
when is there a surge of catecholamines
during delivery
what do catecholamines do
• Raises blood pressure
• Supports energy metabolism
• Aids thermogenesis via brown fat - releasing energy as heat rather than ATP
- thyroid hormone surge has similar effects
how do babies maintain heat
- chest contact
- thermaingoen in brown adipose tissue
what is the main supply of food for the baby in utero and after birth
- glucose in utero
- after birth it is free fatty acids
describe metabolic changes that the baby undergoes
- in babies nutritional supply from placenta stops at brith and blood glucose levels fall
- Reduction in insulin rise in glucagon and catecholamines
- Newborns tolerate lower blood sugar levels (normal low 2-2.6mmol/L)
- The use alternative energy soruces such as ketone bodies, free fatty acids
- Term neonates have laid down fat and glycogen reseveres
what are babies more suspectible to in gestational diabetes
- more likely to get hypoglycaemia
- pancreas is using a lot of insulin in the womb to get rid of glucose but then there is a sugar drop and no sugar for the baby to use insulin in so they are more likely to get hypoglycaemia
what is the rooting reflex
stroke their bottom lip or cheek they will think it is the breast and they will settle down
when should babies pass meconium
within 48 hours
- transition to milk stools within the first few days this is yellow and grey poo
- If they don’t pass within 48 hours have ot thing about diseases such as blockages or cystic fibrosis
what happens if the baby is stressed in utero
if the baby is stress.in utero they poo inside, this can go into the lungs and cause damage which reduces surfactant
what happens to haematological changes during pregnancy
- Low oxygen levels in-utero. To overcome this:
* Foetus and neonate have higher red blood cell levels (160-220 g/L)- Foetal haemoglobin has higher affinity for O2
- Hemopoiesis transitions from extra-medullary sites (liver) to bone marrow
- Postnatally, HbF decreases by ~6 months
- Clotting is variable – don’t really cross the placenta
- Clotting factors don’t cross the placenta and neonates will have lower values than adults
- Neonates are deficient in vitamin K so receive supplementation at birth – inejctoin or oral supplement – some are at risk of having haemorrhoid
what is foetal haemoglobin made out of
Foetal haemoglobin – 2 alpha 2 gamma
what is adult haemoglobin made out of
Adult haemoglobin – 2 alpha and 2 beta
why is the baby anaemic at 2 months
baby seen anaemic at 2 months due to the switch in haemoglobin
what causes neonatal jaundice
- The breakdown of foetal red cells results in high levels of bilirubin
- Poor activity of hepatic glucuronyl transferase leads low levels of conjugation and excretion
- Therefore, neonatal jaundice is common
- Red cells start breaking down as soon as the baby is out and haemoglobin is breaking down and bilirubin is being formed
- Goes to the liver to get conjgualted by glucuronyl transverase so it can be excreted but glucuronyl transferase is not up to the job so bilirubin is not conjgulated
- Therefore jaundice develops
what is the worry with jaucine
- Worry if the bilirubin goes very high, can start depositing itself in the brain and cause cerberoplasy –
how do you treat jaundice
use blue phototerhapy lights to treat it, it swtiches the chemical formation of the bilirubin molecule so the kidneys can excrete it without conjugulation
what time is urine produced from
- it is produced from around 16 weeks gestation
where is urine produced form
- it is produced from the kidney
what does the placenta do for the kidney
it maintains many of the kidneys functions such as
- excretion
- acid base balance
what does nephrogensis completed by
approximately 34 weeks gestation
what are babies full of in utero
- 80-90% water in utero
why do babies have a natural weight loss when they are born
- because they loose some of there water that they had in Vitor
what happens to babys and renal blood flow
- there is an increase in renal blood flow this further increases GFR which continues till mature until 1 month of age
how does urine output in a newborn baby work
- Urine output is low on day 1, but all babies should pass urine within 24 hours – if they haven’t do they have an infection, are they dehydrated
when does diuresis establish itself
- it establishes itself within the first few days with increase in urine output and loss of water
can babys produce concentrated urine
– the baby is less able concentrate urine and excrete molecules – in healthy term baby don’t have to worry about this, issue in preterm babies and unwell term babies, if you give then tons of salt the kidney cannot regulate this
does the baby have a immune system in utero
In-utero, the foetus is relatively immunosuppressed given its dependence on mother
what does the immune system primarily rely on postnatally
- innate immune system - although has less capability to mount neutrophil response
- maternally-derived IgG
describe the other parts of the immune system of the baby
Cell-mediated immunity favours T-helper cell response, increasing vulnerability to certain infections
Limited humoral response – low IgA, IgM levels
Gains immune benefit from breastmilk
IgA found in mucosal surfaces, complement, lactoferrin, lysozyme
what are the disruption to normal transition
- Prematurity
- Other disease states in baby, e.g. congenital abnormalities, infection, asphyxia
- Non-labour deliveries, e.g. elective caesareans – baby hasn’t had a chance to do all hormone, it can go into respiratory distress
- Complicated deliveries
- Maternal health and medications (including anaesthesia) – baby can be anaesthetised when it comes outs
