Adaptation at Birth Flashcards
What may a streaky CXR soon after birth indicate has happened during foetal adaptation?
Meconium Aspiration syndrome
=> bits of meconium are blocking the airways
What are the main roles of the placenta which all need to be adapted by the foetus after birth?
- gas exchange
- waste transport
- acid-base balance
- hormones (these prepare the foetus for adaptation)
- IgG transport
Describe the foetal circulation in utero
- O2 blood from mum to baby via umbilical vein
- flows through Liver via ductus venosus
- into IVC
- RA -> foramen ovale -> LA -> aorta
- DeO2 blood passes to umbilical arteries (coming off iliacs) and flows back to mum
- some blood does not pass through foramen ovale => goes to RV
- this is ejected via pulmonary trunk
- due to high pulmonary resistance, most flows through the patent ductus arteriosus to the aorta
What does the ductus venosus become in the liver?
Ligamentum Teres
How much of the maternal blood delivered to the foetus actually reaches the foetal lungs?
Only around 7% due to fluid filled lungs creating high pulmonary resistance
How does a baby prepare for birth in its 3rd trimester?
- Surfactant production
- Accumulation of glycogen – liver, muscle, heart
- Accumulation of brown fat – between scapulae and around internal organs
- Accumulation of subcutaneous fat
- Swallowing amniotic fluid
How does surfactant help breathing and where is it produced?
- Phospholipid made in Type II Pneumocyte cells of alveoli
- Helps alveoli fill up with air more (rather than being stiff like the first time you blow up a balloon)
Why does glycogen accumulate in preparation for birth?
- Body gets ready for a period of starvation after leaving the womb as milk may not be readily available
Why do babies accumulate “Brown fat” in the last trimester?
- Insulation
=> protects them from becoming cold after leaving the womb
Why do babies swallow amniotic fluid before leaving the womb?
- helps to grow and expand lungs
- practising breathing
- If baby has only swallowed a small amount of fluid, often the lungs are small and “plastic-like”
During labour and delivery, how does the baby adapt its lungs?
Synthesis of lung fluid stops
Vaginal delivery – squeezes lungs => 30 of the 100ml of fluid is expelled from the lungs
Describe how the baby looks in the first few seconds after birth, and why this occurs?
Blue
Starts to breathe
Cries to help oxygenate the lungs and change to “adult” circulation
Gradually goes pink once this circ. kicks in
Cord cut after delayed clamping
What factors cause the foetal circulation to change after birth?
Pulmonary vascular resistance drops (as there is now air and not fluid in the lungs)
Systemic vascular resistance rises (as cord is clamped => back pressure from umbilical arteries)
O2 tension rises
Circulating prostaglandins drop (due to hormone release and back pressure of blood flow)
Ductus arteriosus and Foramen ovale close
A patent foramen ovale may cause a physiological murmur for a day or two until closure. TRUE/FALSE?
TRUE
What factors can cause failure of cardio-respiratory adaptation in the newborn?
Placental dysfunction
=> change in acid-base balance
=> Baby is not going to be prepared to take first breath or keep warm as it has already used up glycogen stores attempting to combat AB imbalance
Preterm Birth
- baby has not had enough time in 3rd trimester to build up adequate stores or prepare themself for the adaptation to extra-utero world
What is Persistant Pulmonary Hypertension of the Newborn (PPHN) and why does it occur?
- if lungs are still solid/full of fluid => high pulmonary resistance
- Pulmonary resistance > systemic resistance => blood is going to travel to systemic circ via patent duct and foramen ovale
=> NO O2 will be picked up at the lungs to oxygenate the blood
How is PPHN investigated?
Pre and post ductal saturation monitoring
- Circulation to R arm comes off aorta BEFORE introduction of blood from patent ductus arteriosus
=> Sats monitor reading on R hand is compared to sats monitor on left foot (usually)
- if difference >3% the there is an increased risk of PPHN
How can PPHN be managed?
Ventilation
Oxygen
Nitric oxide (given from ventilator - dilates pulmonary vasculature)
Sedation (given as babies can try to breath against the ventilator)
Inotropes (to regulate stroke volume)
ECLS (Extracorporeal Life Support - 2 central lines - only done at specialised centres due to high risk of hypocoagulable state)
What is Transient Tachypnoea of the Newborn and what babies normally develop this?
- Babies born by C-section do not experience lung squeeze to get rid of fluid
=> they take longer to absorb their own lung fluid
=> grunt when breathing
=> Treated as if infection until proven otherwise
What are the main aims of a newborn baby in the first few hours?
Thermoregulation
Glucose homeostasis
Nutrition
Why do babies easily get cold?
Can lose heat by 4 mechanisms:
- Radiation (from head as this has large surface area in comparison to body)
- Convection (i.e. from draughts - as they are often wet when they are born)
- Evaporation (as above)
- Conduction (warm baby on a cold surface will dissipate heat
Why do babies struggle to regulate their own temperature?
- They cannot shiver if they get cold
- Heat is produced by breakdown of stored brown adipose tissue in response to catecholamines
- This is NOT efficient in the first 12 hours of life
Why are SGA/preterm babies at a higher risk of hypothermia?
- Low stores of brown fat
- Little subcutaneous fat
- Larger surface area:vol
How can hypothermia in babies be minimised?
- Keep them Dry
- Hat
- Skin to skin contact
- Blanket / clothes
- Heated Mattress
- Incubator
If babies glycogen stores are depleting after being born, what can be used as brain fuel instead of glucose?
Ability to use ketones as brain fuel
Why may a baby be born hypoglycaemic?
Increased energy demands due to:
- Unwell
- Hypothermia
Low glycogen stores due to:
- Small, premature
Inappropriate insulin / glucagon ratio if:
- Maternal diabetes
- Hyperinsulinism
Some drugs
The hormones present when a mother breastfeeds are thought to counteract post-natal depression. TRUE/FALSE?
TRUE
- breast feeding increases the presence of “happy hormones”
HOw does breast milk composition change?
Colostrum (quenches thirst)
Foremilk and hindmilk (different make-ups)
A baby’s weight will naturally decrease slightly before aligning on a centile. TRUE/FALSE?
TRUE
- it is a worry if babys begin to cross centiles
Describe the difference between foetal and adult Hb?
Foetal Hb = higher affinity for O2
BUT not so good at letting go of it
What compound allows shift of the haemoglobin curve to the right?
Increase in 2,3 BPG shifts curve to right
What other haematological changes take place during foetal adaptation?
Haematopoiesis moves to bone marrow from the liver
Why may any baby have anaemia if a Hb reading is taken between 8-10 weeks?
Foetal Hb is being broken down
Adult Hb only starting to be produced
What are the risk factors for adaptation problems at birth?
- Hypoxia / asphyxia during delivery
- small or large babies
- Premature babies
- Some maternal illnesses and medications
- Ill babies – sepsis, congenital anomalies
