1: Perinatal Adaptation I

Question 1

What colour are babies when they’re born?

Why?

Answer 1

Blue (cyanotic)

Hypoxic, deflated lungs

Question 2

Swallowing amniotic fluid is a normal part of foetal homeostasis.

What condition can be caused by swallowing amniotic fluid following or during foetal distress?

Answer 2

Meconium aspiration syndrome

causes ARDS - meconium clogs up air spaces and neonate will become hypoxic

Question 3

At what point in gestation do the alveoli develop?

Answer 3

36 weeks

So prematurity requires steroids to speed up lung development

Question 4

What is produced from 26 weeks and is required for lung development?

Answer 4

Pulmonary surfactant

Question 5

What is the purpose of pulmonary surfactant?

Which cells produce it?

Answer 5

Reduce alveolar surface tension, allowing them to resist collapse

Type II pneumocytes

Question 6

What does amniotic fluid consist of

a) early in the pregnancy
b) later in the pregnancy?

Answer 6

a) Maternal fluid
b) Foetal urine

Question 7

A lack of amniotic fluid in the womb is related to a problem with which organs?

Answer 7

Kidneys

involved in amniotic fluid recycling

Question 8

Which organs allow a baby to swallow and then filter amniotic fluid?

Answer 8

Kidneys

Question 9

Why do babies cry when they are born?

Answer 9

Forcing air against a closed glottis pushes fluid from the air spaces to the interstitium

Question 10

Which maternal antibody is passed across the placenta to the foetus?

Answer 10

IgG

Question 11

In the first 10 - 20 minutes of life, is oxygen used to resuscitate babies?

Answer 11

No

Does more harm than good

Question 12

How long should you wait before clamping a newborn’s umbilical cord?

Why?

Answer 12

3 - 5 minutes

Allows adequate transfer of blood - clamping too early can lead to hypovolaemia and anaemia

Question 13

What are the three shunts in the foetal circulation?

Answer 13

Ductus venosus (bypassing the liver)

Foramen ovale (right to left shunt in the heart)

Ductus arteriosus (bypassing pulmonary circulation)

Question 14

In the foetus, the pulmonary circulation has a (high / low) resistance.

Answer 14

high resistance

Question 15

Does blood travel to the lungs in the foetus?

Answer 15

Yes

But a v small amount (around 7%), most of it is shunted from R heart to L heart

Question 16

How many umbilical arteries and veins does a foetus have?

Which type of blood travels in each?

Answer 16

1x umbilical vein - OXYGENATED BLOOD FROM MOTHER

2x umbilical arteries - DEOXYGENATED BLOOD FROM FOETUS

Question 17

Describe the pulmonary vascular resistance before birth.

Answer 17

High

Allows very little blood to travel to the lungs

Question 18

Describe the systemic vascular resistance before birth.

Answer 18

Low

Especially compared to the pulmonary resistance

Addition of placenta adds a massive ‘length’ to vasculature, reducing the resistance

Question 19

What remnants of the

a) ductus venosus
b) foramen ovale
c) ductus arteriosus

can be found in adults?

Answer 19

a) Ligamentum teres of the liver

b) Oval fossa

c) Ligamentum arteriosum

Question 20

Why does the foramen ovale close after birth?

Answer 20

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

Question 21

What three factors contribute to the closing of the ductus arteriosus?

Answer 21

1. Reduced blood flow

2. Reduced Prostaglandin E2 produced by placenta

3. Smooth muscle CONTRACTS (unique response not found anywhere else)

Question 22

After birth, the smooth muscle of the ductus arteriosus (relaxes / constricts).

Answer 22

constricts to reduce blood flow through shunt

Question 23

Which chemical maintains the patency of the ductus arteriosus?

Which organ produces it?

Answer 23

Prostaglandin E2

Placenta

Question 24

Why does systemic vascular resistance decrease following birth?

Answer 24

Widespread vasodilation caused by oxygen

Loss of the ‘length’ of the placental circulation

Question 25

Why does **pulmonary vascular resistance** drop following birth?

Answer 25

**Lungs inflate** **Oxygen is a vasodilator --\> widespread vasodilation of the pulmonary vasculature**

Question 26

Which form of **glucose** is stored by the foetus before birth? What is the advantage of this?

Answer 26

**Glycogen** Loads of sugar stored for first few days post-natally

Question 27

Which type of fat can be rapidly oxidised to produce energy?

Answer 27

**Brown fat**

Question 28

Which process is brown fat useful for?

Answer 28

**Thermogeneration** making heat

Question 29

What is the function of a) white fat b) brown fat?

Answer 29

**a) Energy storage** **b) Thermogeneration**

Question 30

Where is **brown fat** found in the foetus?

Answer 30

**Between scapulae** **Around viscera**

Question 31

What diseases, relating to foetal shunts, can cause congenital heart disease in newborns?

Answer 31

**Patent foramen ovale** **Patent ductus arteriosus** **Persistence of foetal circulation**

Question 32

What happens to the levels of **Prostaglandin E2** on birth?

Answer 32

**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

Question 33

Being born too **(early / late)** can cause hypoxia - why?

Answer 33

**Too early** No time for foetal adapations (e.g pulmonary surfactant) to occur

Question 34

What **metabolic disorder** is caused by **foetal distress?**

Answer 34

**Metabolic acidosis** Foetal distress is hypoxia; switch to anaerobic respiration; production of excess lactic acid

Question 35

Newborns need to be protected from **(heat / cold).** ## Footnote **Why?**

Answer 35

**cold** 'cold stress' - newborns need careful thermoregulation as they easily become hypothermic

Question 36

What condition can **persistence of foetal shunts** cause?

Answer 36

**Persistent pulmonary hypertension**

Question 37

Which investigation can be used to diagnose persistent pulmonary hypertension?

Answer 37

**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)

Question 38

How is **persistent pulmonary hypertension** managed?

Answer 38

**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

Question 39

The key in managing persistent pulmonary hypertension is raising the **\_\_\_ pressure** above the **\_\_\_ pressure.**

Answer 39

**raise systemic/peripheral pressure** ABOVE **pulmonary pressure** to abolish R\>L shunt and let the ductus arteriosus close use oxygen, nitric oxide, inotropes

Question 40

Which **respiratory illness** is seen in many newborns and resolves with time?

Answer 40

**Transient tachypnoea**

Question 41

What causes **transient tachypnoea** in newborns?

Answer 41

**Impaired clearance of fluid from the lungs**

Question 42

Why might a newborn develop **transient tachypnoea?**

Answer 42

**Pre-mature delivery** - inadequate time to produce pulmonary surfactant

Question 43

How do we generate heat when we're cold?

Answer 43

**Shivering** primarily Some heat energy from metabolism as well

Question 44

By which process do **newborns** produce heat?

Answer 44

**Non-shivering thermogenesis**

Question 45

What tissue do **newborns** use to produce heat?

Answer 45

**Brown fat**

Question 46

Why are **small-for-dates** or **pre-term newborns** more likely to suffer **cold stress?**

Answer 46

**Less brown fat to produce heat with** They need wrapped up / heated / incubated

Question 47

In the first few days after birth, mature newborns require a small volume of colostrum and can regulate their own blood glucose levels. Why?

Answer 47

**Large stores of glycogen built up during pregnancy**

Question 48

Why may newborns become **hypoglycaemic**?

Answer 48

**Increased energy demands:** illness, cold stress **Inadequate glycogen stores:** small-for-dates or pre-term **Maternal diabetes** **Maternal medication**

Question 49

What is the **rooting reflex**?

Answer 49

When something touches baby's mouth or lips, it reflexively tries to open its mouth and attach to it

Question 50

What is the **sucking reflex**?

Answer 50

When something touches the baby's palette, the baby will reflexively try to suck on it

Question 51

How is the growth of a baby measured after birth?

Answer 51

**Growth chart**

Question 52

What are the differences between **foetal Hb** and **adult Hb**?

Answer 52

**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

Question 53

Where is **foetal Hb** produced?

Answer 53

**Liver**

Question 54

Where is **adult Hb** produced?

Answer 54

**Bone marrow**

Question 55

What happens to the ratio of **foetal Hb : adult Hb** after birth?

Answer 55

**Foetal Hb is broken down** **Adult Hb is produced**

Question 56

Why can **newborns** become anaemic?

Answer 56

**Foetal Hb is broken down** FASTER **than Adult Hb is produced**

Question 57

Just after birth, **foetal Hb is broken down** while **adult Hb is produced in the bone marrow.** What is produced by Hb breakdown?

Answer 57

**Bilirubin**

Question 58

What signs does the accumulation of bilirubin cause?

Answer 58

**Yellow skin and conjunctiva** **Dark, yellow urine** **Pale stools**

Question 59

The accumulation of **\_\_\_ bilirubin** causes **jaundice** in newborns. Why?

Answer 59

**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

Question 60

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**?

Answer 60

**a) Rooting reflex** **b) Sucking reflex**