Perinatal Adaptation

Question 1

What is the function of the placenta?

Answer 1

Foetal homeostasis 
Gas exchange
Nutrient transport
Waste product transport 
Acid base balance 
Hormone production (prepares for labour)
Transport of IgG

Question 2

Describe the foetal circulation

Answer 2

1. Oxygenated blood from placenta
2. Umbilical vein
3. Ducuts venosus in liver
4. IVC
5. Foramen ovale
6. Left ventricle and aorta
7. Right ventricle
8. Ducuts arteriosus and aorta or pulmonary vein to lungs

Question 3

What does deoxygenated blood leave by?

Answer 3

Umbilical arteries

Question 4

During the third trimester how does the baby prepare for birth?

Answer 4

Surfactant production (reduce surface tension to aid gas exchange)
Accumulation of glycogen (ready for starvation state)
Accumulation of brown fat (insulating internal organs)
Accumulation of subcutaneous fat (insulation)
Swallowing/inhaling amniotic fluid (fills lungs to aid growth)

Question 5

How does the baby respond to labour to aid delivery?

Answer 5

Increases catecholamines/cortisol to prepare for stress
Synthesis of lung fluid stops
Vaginal delivery - lungs squeeze to get rid of fluid

Question 6

How much fluid is lost by lung squeezing?

Answer 6

30%

Question 7

How does the baby lose most of the fluid?

Answer 7

Crying - 70% is lost by absorption of fluid to lymphatics

Question 8

In the first few seconds of life how does a baby adapt to the new world?

Answer 8

Comes out blue, starts to breath and cry, gradually goes pink (oxygenation), cord cut

Question 9

What does a delay in cord cutting allow?

Answer 9

Blood volume to increase and transfer of immunoglobulins

Question 10

Describe cardiorespiratory adaptation after birth

Answer 10

• PVR drops while SVR rises
• Back pressure slows flow across foramen ovale and ductus arteriosus (blood flows more easily to lungs)
• Oxygen tension rises
• Prostaglandins decrease to contract ducts and close foramen ovale

Question 11

What do the two foetal ducts become?

Answer 11

ductus arteriosus - ligamnetum arteriosus

ductus venosus - ligamentum teres

Question 12

What can failure of cardiorespiratory adaptation lead to?

Answer 12

Persistent Pulmonary Hypertension of the Newborn

Question 13

Describe the pathogenesis of PPHN

Answer 13

1. High PVR as the lungs are solid/no surfactant and will not open
2. Oxygenation is minimal and shunts remain open - mixed blood travels to the body

Question 14

How can you test for an open ductus arteriosus?

Answer 14

Preductal arteries will have higher oxygenation than post ductal arteries - by testing saturation of right hand and one of the feet >3% difference indicates pathology

Question 15

How is PPHN treated?

Answer 15

Ventilation to give oxygen
Nitric Oxide - dilates pulmonary vasculature to decrease resistance
Sedation - stops the baby breathing against the ventilator
Inotropes - help cardiac function
Extracorpeal membrane oxygenation

Question 16

Who often presents with transient tachypnoea?

Answer 16

Full term babies born by C -section

Question 17

How does transient tachypnoea arise?

Answer 17

Lack of lung squeeze (in vaginal delivery) means fluid builds up in the lungs.

Question 18

What happens to babies with transient tachypnoea?

Answer 18

Usually gets better relatively quickly but requires an infection screening and occasionally respiratory support

Question 19

Why is it hard for babies to regulate their temperature?

Answer 19

Large surface area (big head)
Wet when they are born (evapouration)
Babies cannot shiver

Question 20

How is heat lost in babies?

Answer 20

Evaporation
Conduction
Convection
Radiation

Question 21

Define acrocyanosis

Answer 21

Persistent blue extremities, peripheral vasoconstriction and adapting circulation

Question 22

What is the ideal temperature range for a baby?

Answer 22

36.5-37.4

Question 23

How are babies kept warm?

Answer 23

Dried, hat, skin to skin contact, blanket/clothes, heated mattress, incubator

Question 24

What happens to the glucose levels when a baby is born?

Answer 24

When glucose from the placenta is lost there is a physiological drop in insulin to allow an increase in glycogen - mobilisation of hepatic stores for gluconeogenesis

Question 25

What can be used as brain fuel in babies - short term?

Answer 25

Ketones

Question 26

What causes hypoglycaemia?

Answer 26

Increased demand - unwell, hypothermic
Low glycogen stores - small/premature
Inappropriate insulin/glucagon ratio - maternal diabetes/hyperinsulinaemia
Labetalol

Question 27

Describe the different types of haemoglobin

Answer 27

Foetal Hb has a high affinity for oxygen but is not so good at letting it go. After birth a chemical changes foetal Hb to adult Hb

Question 28

Where are the two types of haemoglobin produced?

Answer 28

Foetal - liver

Adult - bone marrow

Question 29

How does anaemia arise in babies?

Answer 29

Adult Hb is synthesised slower than foetal Hb is broken down