Week 5- adaptions at birth

Question 1

By which transport method do things move into/out of the placenta?

Answer 1

Diffusion

Question 2

What saturations does foetal oxygenated blood have?

Answer 2

80%.

Question 3

What immunoglobulin gives the baby passive immunity?

Answer 3

IgG

Question 4

What is the function of the placenta?

Answer 4

Fetal homeostasis
Gas exchange
Nutrient transport to the fetus 
Waste product transport from fetus
Acid base balance
Hormone production
Transport of IgG

Question 5

Which hormones does the placenta produce?

Answer 5

Insulin and insulin like growth factor
Glucocorticosteroids
Placental lactogen

Question 6

What is the function of insulin and insulin like growth factor in the fetus?

Answer 6

Essential for growth.

Question 7

What substance is responsible for growth of the placenta?

Answer 7

IgF 2.

Question 8

What is the function of glucocorticosteroids?

Answer 8

They are basically the opposite to insulin and insulin like growth factor where they restrict fetal growth, however allow the specialisation of tissues

Question 9

What is the function of placental lactogen in the fetus? Which types of pregnancy will this hormone be increased in?

Answer 9

Has anti-insulin effects.

Multiple pregnancies to keep the babies small so they can fit.

Question 10

What does the umbilical vein carry and where does it go in the fetus before birth?

Answer 10

Umbilical vein carries oxygenated blood from the placenta to the liver.

Question 11

Where is the ductus venosus and what does it bypass and why?

Answer 11

Ductus venosus is between the umbilical vein and the inferior vena cava. This means the oxygenated blood bipasses the liver.

Question 12

Describe the blood in the IVC after the ductus venosus?

Answer 12

Here you have mixing of oxygenated blood from the umbilical vein with deoxygenated blood from the limbs, so its a mix.

Question 13

Describe the flow of blood through the fetal heart?

Answer 13

Blood enters the right atrium and has two options:
Some of it goes into the right ventricle and is then pumped into the pulmonary artery.
Some of it goes through the foramen ovale and into the left atrium to be pumped into the left ventricle and out to the body.

Question 14

Describe the pulmonary arteries adaptations in the fetus?

Answer 14

The lungs aren’t being used so have a lot of resistance causing pressure in the pulmonary artery to be high. This means only a small amount of blood (7%) goes to the lungs. The rest of the blood goes through the ductus arterioles to the aorta to be pumped around the rest of the body.

Question 15

How does blood go back to the placenta?

Answer 15

The umbilical arteries.

Question 16

In the 3rd trimester, what adaptations does the fetus do in preparation for birth?

Answer 16

Surfactant production
Accumulation of glycogen- needs energy stores
Accumulation of brown fat- around scapulae and heart
Accumulates subcutaneous fat
Swallows amniotic fluid- to help its lungs develop.

Question 17

During labour, what physiological reactions does the fetus have?

Answer 17

Produces catecholamines and cortisol to increase its metabolic rate.
Stops synthesising lung fluid- reabsorbs sodium to reabsorb remaining fluid
In vaginal delivery- the lungs are squeezed.

Question 18

What does the baby do in the first few seconds of life?

Answer 18

Starts blue
Starts to breathe
Cries
Gradually goes pink (over about 5 mins)

Question 19

Describe how the foramen ovale closes after birth?

Answer 19

The pulmonary resistance drops and systemic vascular resistance rises. This means pressure in the left side of the heart is now higher than the right.
Also circulating prostaglandins drop and oxygen tension rises causing the duct to close.

Question 20

What does the ductus arteriosus become?

Answer 20

Ligamentum arteriosus

Question 21

What does the ductus venosus become?

Answer 21

Ligamentum teres.

Question 22

Which babies are at risk of cardiorespiratory abnormalities?

Answer 22

Preterm babies
Assisted delivery babies
Babies with infections
Babies who pass meconium during birth.

Question 23

What is persistent pulmonary hypertension of the newborn? What is the issue with this?

Answer 23

The two shunts- foramen ovale and ductus arteriosus persist.
There is no longer any oxygenated blood coming from the placenta so you get deoxygenated blood coming into the left ventricle and being pumped around the body.
Also there is very little blood going to the lungs so you can’t oxygenate it properly.

Question 24

How can you test for persistent pulmonary hypertension of the newborn?

Answer 24

Oxygen saturations in the arms will be 5-10% different to the legs because they are the first branches of the aorta.

Question 25

How do you manage persistent pulmonary hypertension of the newborn?

Answer 25

Ventilation
Oxygen
Nitric oxide
Sedation

If all else fails heart lung bypass

Question 26

What is transient tachyopneoa?

Answer 26

If the fluid in the lungs doesn’t drain properly. The switch from fluid excretion to sodium reabsorption hasn’t completed then fluid will persist in the lungs.

Question 27

What three things are important in the first few hours of babies life?

Answer 27

Thermoregulation- have to keep the baby warm
Glucose homeostasis- have to keep the babies blood sugar up
Nutrition- to grow.

Question 28

How do you keep the baby warm after birth?

Answer 28

Dry it- babies are wet when they come out
Skin- skin contact with mum
Dry warm towel so they can’t lose heat from convection and radiation.

Question 29

What four ways can babies lose heat?

Answer 29

Convection
Conduction- to objects
Radiation
Evaporation

Question 30

How do babies generate heat?

Answer 30

They are unable to shiver.
They do non-shivering thermogenesis- heat is produced by the breakdown of stored brown adipose tissue in response to catecholamines.
Peripheral vasoconstriction.

NOTE- these methods don’t work in the first few hours of life.

Question 31

Why are small for dates babies more at risk of hypothermia?

Answer 31

They haven’t got as much brown adipose tissue.
Little subcutaneous fat
Larger surface area to volume ratio

Question 32

Why is glucose homeostasis disrupted at birth?

Answer 32

The baby goes from having a constant infusion from the mum to not having any at all.
There is also a drop in insulin and an increase in glycogen.
Very little oral intake of breast milk.

Question 33

In what situations can babies become hypoglycaemic?

Answer 33

Small for dates- not a substantial stored energy supply
Mother had diabetes- goes from having so much blood sugar and accounting for this by producing so much insulin to having a lower blood sugar but with the same large insulin supply.
Increased energy demands- if the baby is hypothermic or unwell.

Question 34

How does suckling stimulate the mother to produce milk?

Answer 34

Sensory signals go from the nipple to the hypothalamus. This sends signals to the posterior pituitary causing release of oxytocin meaning milk is ejected. Also sends signals to the anterior pituitary causing release of prolactin meaning milk is produced.

Question 35

What causes the change in fetal haemoglobin to adult haemoglobin?

Answer 35

An increase in 2, 3 DPG

Question 36

What issues can arise with a change from fetal to adult haemoglobin?

Answer 36

Adult haemoglobin is produced a lot slower than fetal haemoglobin undergoes haemolysis- this can lead to temporary anaemia. This presents as physiological jaundice.

Question 37

What causes physiological jaundice?

Answer 37

Fetal haemoglobin breakdown
Conjugating pathways immature
Rise in circulating unconjugated bilirubin.