Adaptation at Birth

Question 1

What may a streaky CXR soon after birth indicate has happened during foetal adaptation?

Answer 1

Meconium Aspiration syndrome

=> bits of meconium are blocking the airways

Question 2

What are the main roles of the placenta which all need to be adapted by the foetus after birth?

Answer 2

• gas exchange
• waste transport
• acid-base balance
• hormones (these prepare the foetus for adaptation)
• IgG transport

Question 3

Describe the foetal circulation in utero

Answer 3

• 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

Question 4

What does the ductus venosus become in the liver?

Answer 4

Ligamentum Teres

Question 5

How much of the maternal blood delivered to the foetus actually reaches the foetal lungs?

Answer 5

Only around 7% due to fluid filled lungs creating high pulmonary resistance

Question 6

How does a baby prepare for birth in its 3rd trimester?

Answer 6

• 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

Question 7

How does surfactant help breathing and where is it produced?

Answer 7

• 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)

Question 8

Why does glycogen accumulate in preparation for birth?

Answer 8

• Body gets ready for a period of starvation after leaving the womb as milk may not be readily available

Question 9

Why do babies accumulate “Brown fat” in the last trimester?

Answer 9

• Insulation

=> protects them from becoming cold after leaving the womb

Question 10

Why do babies swallow amniotic fluid before leaving the womb?

Answer 10

• 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”

Question 11

During labour and delivery, how does the baby adapt its lungs?

Answer 11

Synthesis of lung fluid stops

Vaginal delivery – squeezes lungs => 30 of the 100ml of fluid is expelled from the lungs

Question 12

Describe how the baby looks in the first few seconds after birth, and why this occurs?

Answer 12

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

Question 13

What factors cause the foetal circulation to change after birth?

Answer 13

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

Question 14

A patent foramen ovale may cause a physiological murmur for a day or two until closure. TRUE/FALSE?

Answer 14

TRUE

Question 15

What factors can cause failure of cardio-respiratory adaptation in the newborn?

Answer 15

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

Question 16

What is Persistant Pulmonary Hypertension of the Newborn (PPHN) and why does it occur?

Answer 16

• 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

Question 17

How is PPHN investigated?

Answer 17

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

Question 18

How can PPHN be managed?

Answer 18

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)

Question 19

What is Transient Tachypnoea of the Newborn and what babies normally develop this?

Answer 19

• 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

Question 20

What are the main aims of a newborn baby in the first few hours?

Answer 20

Thermoregulation
Glucose homeostasis
Nutrition

Question 21

Why do babies easily get cold?

Answer 21

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

Question 22

Why do babies struggle to regulate their own temperature?

Answer 22

• 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

Question 23

Why are SGA/preterm babies at a higher risk of hypothermia?

Answer 23

• Low stores of brown fat
• Little subcutaneous fat
• Larger surface area:vol

Question 24

How can hypothermia in babies be minimised?

Answer 24

• Keep them Dry
• Hat
• Skin to skin contact
• Blanket / clothes
• Heated Mattress
• Incubator

Question 25

If babies glycogen stores are depleting after being born, what can be used as brain fuel instead of glucose?

Answer 25

Ability to use ketones as brain fuel

Question 26

Why may a baby be born hypoglycaemic?

Answer 26

Increased energy demands due to:

• Unwell
• Hypothermia

Low glycogen stores due to:
- Small, premature

Inappropriate insulin / glucagon ratio if:

• Maternal diabetes
• Hyperinsulinism

Some drugs

Question 27

The hormones present when a mother breastfeeds are thought to counteract post-natal depression. TRUE/FALSE?

Answer 27

TRUE

- breast feeding increases the presence of “happy hormones”

Question 28

HOw does breast milk composition change?

Answer 28

Colostrum (quenches thirst)

Foremilk and hindmilk (different make-ups)

Question 29

A baby’s weight will naturally decrease slightly before aligning on a centile. TRUE/FALSE?

Answer 29

TRUE

- it is a worry if babys begin to cross centiles

Question 30

Describe the difference between foetal and adult Hb?

Answer 30

Foetal Hb = higher affinity for O2

BUT not so good at letting go of it

Question 31

What compound allows shift of the haemoglobin curve to the right?

Answer 31

Increase in 2,3 BPG shifts curve to right

Question 32

What other haematological changes take place during foetal adaptation?

Answer 32

Haematopoiesis moves to bone marrow from the liver

Question 33

Why may any baby have anaemia if a Hb reading is taken between 8-10 weeks?

Answer 33

Foetal Hb is being broken down

Adult Hb only starting to be produced

Question 34

What are the risk factors for adaptation problems at birth?

Answer 34

• Hypoxia / asphyxia during delivery
• small or large babies
• Premature babies
• Some maternal illnesses and medications
• Ill babies – sepsis, congenital anomalies