Foetal Adaptation at Birth

Question 1

What are the three shunts in the foetal circulation?

Answer 1

Ductus venosus (portal circulation)
Foramen ovale (R to L atrium)
Ductus arteriosus (pulmonary artery --> arch of aorta)

Question 2

Which changes occur in the 3rd trimester to prepare the foetus for birth?

Answer 2

Surfactant production
Accumulation of glycogen - liver, muscle, heart
Accumulation of brown fat - between scapulae + around internal organs
Accumulation of subcutaneous fat
Swallowing amniotic fluid

Question 3

Describe the transition from foetal circulation to normal circulation

Answer 3

Pulmonary vascular resistance drops
Systemic vascular resistance rises
Oxygen tension rises
Circulating prostaglandins drop
Duct constricts
Foramen ovale closes

Question 4

What happens to the foramen ovale after birth?

Answer 4

Closes of persists as PFO

Question 5

What happens to the ductus arteriosus after birth?

Answer 5

Becomes ligamentum arteriosus

or persists as PDA

Question 6

What happens to the ductus venosus after birth?

Answer 6

Becomes ligamentum teres

Question 7

Why do newborn babies need help with thermoregulation?

Answer 7

Large surface area
Wet when born
Not able to shiver

Question 8

Why are small for dates/preterm babies more predisposed to hypothermia?

Answer 8

Low stores of brown fat
Little subcutaneous fat
Larger surface area:volume

Question 9

Which methods are used to help prevent/treat hypothermia?

Answer 9

Dry baby
Hat
Skin to skin
Blanket/clothes
Heated mattress
Incubator

Question 10

What are some of the causes of hypoglycaemia in a neonate?

Answer 10

Increased energy demands:
- unwell
- hypothermia
Low glycogen stores:
- small, premature
Inappropriate insulin/glucagon ratio:
- maternal diabetes
- hyperinsulinaemia
Some drugs

Question 11

Why does physiological anaemia occur in neonates and when should be normalise?

Answer 11

Adult Hb synthesised more slowly than Fetal Hb broken down

- nadir at 8-10 weeks

Question 12

Why does physiological jaundice occur?

Answer 12

Breakdown of HbF
Conjugating pathways in liver immature
Rise in circulating unconjugated bilirubin
(not harmful unless very high levels)

Question 13

Which babies are particularly at risk of problems with adaptation?

Answer 13

Hypoxia/asphyxia during delivery
Particularly small or large babies
Premature babies
Some maternal illnesses and medications
Ill babies e.g. sepsis, congenital anomalies