Perinatal Adaptation

Question 1

What are the functions of the placenta?

Answer 1

Foetal homeostasis, gas exchange, nutrient transport, acid-base balance, hormone production, transport of IgG

Question 2

What are the three shunts of the foetal circulation?

Answer 2

Ductus arteriosus, ductus venosus, foramen ovale

Question 3

How much of the output from the heart goes to the lungs in the foetal circulation?

Answer 3

7% of output goes via lungs

Question 4

How does the foetus prepare itself for birth in the third trimester?

Answer 4

Surfactant production and swallowing of amniotic fluid

Accumulation of glycogen, brown fat and subcutaneous fat

Question 5

What foetal changes occur during labour and delivery?

Answer 5

Increased catecholamines/cortisol at onset of labour

Synthesis of lung fluid stops

Question 6

What does a vaginal delivery achieve?

Answer 6

Squeezes lungs to get rid of fluid

Question 7

What occurs during the circulatory transition after birth?

Answer 7

Pulmonary vascular resistance drops and systemic vascular resistance rises
Oxygen tension rises and circulating prostaglandins drop
Duct constricts and foramen ovale closes

Question 8

What are the fates of the foetal shunts?

Answer 8

Foramen ovale = closes or persists as PFO (10%)
Ductus arteriosus = becomes ligamentum arteriosus, may persist as PDA
Ductus venosus = becomes ligamentum teres

Question 9

What is the underlying pathophysiology of persistent pulmonary hypertension of the newborn?

Answer 9

Failure of the foetal circulatory system to adapt = more common in term infants

Question 10

What causes hypoxaemia in persistent pulmonary hypertension of the newborn?

Answer 10

Secondary to extrapulmonary shunting of blood from right to left via patent ductus arteriosus and foramen ovale

Question 11

What are the risk factors for persistent pulmonary hypertension of the newborn?

Answer 11

Meconium aspiration, pneumonia, congenital diaphragmatic hernia

Question 12

What are the symptoms of persistent pulmonary hypertension of the newborn?

Answer 12

Grunting, cyanosis, low oxygen saturation and BP, tachycardia and tachypnoea

Question 13

How is persistent pulmonary hypertension of the newborn diagnosed?

Answer 13

CXR, echo, pulse oximetry, ABG

Question 14

How is persistent pulmonary hypertension of the newborn treated?

Answer 14

Ventilation, oxygen, nitric oxide, sedation, inotropes, extracorporeal life support (ECLS)

Question 15

What are the issues with thermoregulation in newborns?

Answer 15

Large surface areas, wet when born, no shivering, peripheral vasoconstriction

Question 16

What is the main source of heat for newborns?

Answer 16

Non-shivering thermogenesis

Question 17

How do newborns perform non-shivering thermogenesis?

Answer 17

Heat produced by breakdown of stored brown adipose tissue in response to catecholamines = not effective in first 12hrs of life

Question 18

Why are small for date and preterm babies more likely to struggle with thermoregulation?

Answer 18

Low stores of brown fat, little subcutaneous fat, larger surface area to volume ratio

Question 19

How can hypothermia be prevented in a newborn?

Answer 19

Dry baby, hat, skin-to-skin contact, blanket/clothes, heated mattress, incubator

Question 20

Why do newborns struggle with glucose homeostasis?

Answer 20

Interruption of glucose supply from placenta

Very little oral intake of milk

Question 21

What happens to newborns after birth in relation to glucose homeostasis?

Answer 21

Drop in insulin and increase in glycogen

Mobilisation of hepatic glycogen stores for gluconeogenesis

Question 22

What can newborns use as brain fuel in place of glucose?

Answer 22

Have ability to use ketones as brain fuel

Question 23

What are the risk factors for hypoglycaemia?

Answer 23

Increased energy demand = illness, hypothermia
Low glycogen stores = small for date, premature
Inappropriate insulin to glycogen ratio = maternal diabetes, hyperinsulinaemia

Question 24

What reflex is triggered when a baby starts to suckle?

Answer 24

Rooting and Suck reflex = feedback loop causes increase in supply

Question 25

How does the composition of breastmilk change over time?

Answer 25

changes from colostrum to foremilk and hindmilk

Question 26

Why does foetal haemoglobin become disadvantageous?

Answer 26

Increase in 2,3 BPG shifts curve to right

Question 27

Where does haematopoiesis move to after birth?

Answer 27

Bone marrow

Question 28

Why does physiological anaemia occur in newborns?

Answer 28

Adult haemoglobin synthesised more slowly than foetal haemoglobin is broken down = lowest at 8-10 weeks

Question 29

Are liver enzyme pathways present in newborns?

Answer 29

Yes, but they are immature

Question 30

What occurs in physiological jaundice?

Answer 30

Breakdown of foetal haemoglobin = conjugating pathways immature, rise in circulating unconjugated bilirubin, not harmful unless very high levels

Question 31

When may jaundice in a newborn be pathological?

Answer 31

If it occurs early or is prolonged

Question 32

What are the risk factors for adaptation problems?

Answer 32

Hypoxia or asphyxia during delivery
Particularly small or large babies, and premature babies
Ill babies = sepsis, congenital anomalies