1: Perinatal Adaptation I Flashcards
What colour are babies when they’re born?
Why?
Blue (cyanotic)
Hypoxic, deflated lungs
Swallowing amniotic fluid is a normal part of foetal homeostasis.
What condition can be caused by swallowing amniotic fluid following or during foetal distress?
Meconium aspiration syndrome
causes ARDS - meconium clogs up air spaces and neonate will become hypoxic
At what point in gestation do the alveoli develop?
36 weeks
So prematurity requires steroids to speed up lung development
What is produced from 26 weeks and is required for lung development?
Pulmonary surfactant
What is the purpose of pulmonary surfactant?
Which cells produce it?
Reduce alveolar surface tension, allowing them to resist collapse
Type II pneumocytes
What does amniotic fluid consist of
a) early in the pregnancy
b) later in the pregnancy?
a) Maternal fluid
b) Foetal urine
A lack of amniotic fluid in the womb is related to a problem with which organs?
Kidneys
involved in amniotic fluid recycling
Which organs allow a baby to swallow and then filter amniotic fluid?
Kidneys
Why do babies cry when they are born?
Forcing air against a closed glottis pushes fluid from the air spaces to the interstitium
Which maternal antibody is passed across the placenta to the foetus?
IgG
In the first 10 - 20 minutes of life, is oxygen used to resuscitate babies?
No
Does more harm than good
How long should you wait before clamping a newborn’s umbilical cord?
Why?
3 - 5 minutes
Allows adequate transfer of blood - clamping too early can lead to hypovolaemia and anaemia
What are the three shunts in the foetal circulation?
Ductus venosus (bypassing the liver)
Foramen ovale (right to left shunt in the heart)
Ductus arteriosus (bypassing pulmonary circulation)
In the foetus, the pulmonary circulation has a (high / low) resistance.
high resistance
Does blood travel to the lungs in the foetus?
Yes
But a v small amount (around 7%), most of it is shunted from R heart to L heart
How many umbilical arteries and veins does a foetus have?
Which type of blood travels in each?
1x umbilical vein - OXYGENATED BLOOD FROM MOTHER
2x umbilical arteries - DEOXYGENATED BLOOD FROM FOETUS
Describe the pulmonary vascular resistance before birth.
High
Allows very little blood to travel to the lungs
Describe the systemic vascular resistance before birth.
Low
Especially compared to the pulmonary resistance
Addition of placenta adds a massive ‘length’ to vasculature, reducing the resistance
What remnants of the
a) ductus venosus
b) foramen ovale
c) ductus arteriosus
can be found in adults?
a) Ligamentum teres of the liver
b) Oval fossa
c) Ligamentum arteriosum
Why does the foramen ovale close after birth?
Pulmonary vascular resistance drops, so blood goes to the lungs avoiding the shunt
Systemic vascular resistance increases, so it’s harder to shunt blood from right heart to left heart
L pressure holds the valve shut and over time it fuses with the septum
What three factors contribute to the closing of the ductus arteriosus?
1. Reduced blood flow
2. Reduced Prostaglandin E2 produced by placenta
3. Smooth muscle CONTRACTS (unique response not found anywhere else)
After birth, the smooth muscle of the ductus arteriosus (relaxes / constricts).
constricts to reduce blood flow through shunt
Which chemical maintains the patency of the ductus arteriosus?
Which organ produces it?
Prostaglandin E2
Placenta
Why does systemic vascular resistance decrease following birth?
Widespread vasodilation caused by oxygen
Loss of the ‘length’ of the placental circulation
Why does pulmonary vascular resistance drop following birth?
Lungs inflate
Oxygen is a vasodilator –> widespread vasodilation of the pulmonary vasculature
Which form of glucose is stored by the foetus before birth?
What is the advantage of this?
Glycogen
Loads of sugar stored for first few days post-natally
Which type of fat can be rapidly oxidised to produce energy?
Brown fat
Which process is brown fat useful for?
Thermogeneration
making heat
What is the function of
a) white fat
b) brown fat?
a) Energy storage
b) Thermogeneration
Where is brown fat found in the foetus?
Between scapulae
Around viscera
What diseases, relating to foetal shunts, can cause congenital heart disease in newborns?
Patent foramen ovale
Patent ductus arteriosus
Persistence of foetal circulation
What happens to the levels of Prostaglandin E2 on birth?
Levels decrease
Because it’s produced by the placenta, which is clamped after bith
Decreases in levels of Prostaglandin E2 cause the ductus arteriosus to close
Being born too (early / late) can cause hypoxia - why?
Too early
No time for foetal adapations (e.g pulmonary surfactant) to occur
What metabolic disorder is caused by foetal distress?
Metabolic acidosis
Foetal distress is hypoxia; switch to anaerobic respiration; production of excess lactic acid
Newborns need to be protected from (heat / cold).
Why?
cold
‘cold stress’ - newborns need careful thermoregulation as they easily become hypothermic
What condition can persistence of foetal shunts cause?
Persistent pulmonary hypertension
Which investigation can be used to diagnose persistent pulmonary hypertension?
Hand / foot saturations
Right hand - sats will be normal-ish
Left foot - sats will be abnormally low (deoxygenated blood shunting from R to L, bypassing pulmonary circulation, shunting through ductus venosus and tracking to left foot)
How is persistent pulmonary hypertension managed?
Ventilate with O2 and NO - nitric oxide is a vasodilator and will help bring pulmonary pressure down
Inotropes - e.g adrenaline, to raise systemic pressure above pulmonary pressure
Sedation - to reduce the infant’s distress
The key in managing persistent pulmonary hypertension is raising the ___ pressure above the ___ pressure.
raise systemic/peripheral pressure ABOVE pulmonary pressure
to abolish R>L shunt and let the ductus arteriosus close
use oxygen, nitric oxide, inotropes
Which respiratory illness is seen in many newborns and resolves with time?
Transient tachypnoea
What causes transient tachypnoea in newborns?
Impaired clearance of fluid from the lungs
Why might a newborn develop transient tachypnoea?
Pre-mature delivery - inadequate time to produce pulmonary surfactant
How do we generate heat when we’re cold?
Shivering primarily
Some heat energy from metabolism as well
By which process do newborns produce heat?
Non-shivering thermogenesis
What tissue do newborns use to produce heat?
Brown fat
Why are small-for-dates or pre-term newborns more likely to suffer cold stress?
Less brown fat to produce heat with
They need wrapped up / heated / incubated
In the first few days after birth, mature newborns require a small volume of colostrum and can regulate their own blood glucose levels.
Why?
Large stores of glycogen built up during pregnancy
Why may newborns become hypoglycaemic?
Increased energy demands: illness, cold stress
Inadequate glycogen stores: small-for-dates or pre-term
Maternal diabetes
Maternal medication
What is the rooting reflex?
When something touches baby’s mouth or lips, it reflexively tries to open its mouth and attach to it
What is the sucking reflex?
When something touches the baby’s palette, the baby will reflexively try to suck on it
How is the growth of a baby measured after birth?
Growth chart
What are the differences between foetal Hb and adult Hb?
Foetal Hb - greater affinity for oxygen, less 2,3-DPG, more concentrated in foetal circulation
Adult Hb - more 2,3-DPG, less concentrated in foetal circulation
Where is foetal Hb produced?
Liver
Where is adult Hb produced?
Bone marrow
What happens to the ratio of foetal Hb : adult Hb after birth?
Foetal Hb is broken down
Adult Hb is produced
Why can newborns become anaemic?
Foetal Hb is broken down FASTER than Adult Hb is produced
Just after birth, foetal Hb is broken down while adult Hb is produced in the bone marrow.
What is produced by Hb breakdown?
Bilirubin
What signs does the accumulation of bilirubin cause?
Yellow skin and conjunctiva
Dark, yellow urine
Pale stools
The accumulation of ___ bilirubin causes jaundice in newborns.
Why?
unconjugated bilirubin
foetus doesn’t have enough enzymes to conjugate bilirubin at an adequate rate, so unconjugated bilirubin accumulates as the result of foetal Hb breakdown
Which reflexes are described by
a) newborn turns head and opens mouth towards any stimulus to the mouth or lips
b) newborn sucks in response to any stimulus touching the palette?
a) Rooting reflex
b) Sucking reflex
