Foetal Circulation & Adaptation at Birth

Question 1

what are 8 functions of the placenta?

Answer 1

1) fetal homeostasis
2) gas exchange
3) acid base balance
4) nutrient transport to foetus
5) waste product transport from fetus
6) hormone production
7) transport of IgG
8) PGE2

Question 2

what are the lungs like in fetus?

Answer 2

lungs are filled with fluid and unexpanded

Question 3

what is the liver like in foetus?

Answer 3

little role in nutrition and waste management

Question 4

what is the gut like in the foetus?

Answer 4

no in use

Question 5

where does the foetal heart pump blood to and what does it do this via?

Answer 5

to the placenta via the umbilical arteries

Question 6

where does the blood from the placenta go and what does it do this via?

Answer 6

returns to foetus via the umbilical vein

Question 7

what is a challenge for the foetus?

Answer 7

• oxygenated, nutrient rich blood returns from placenta to right side of heart & needs to be distributed to growing foetus

Question 8

what are the 3 shunts specific to foetal life?

Answer 8

1) ductus venosus
2) foramen ovale
3) ductus arteriosus

Question 9

what does the ductus venosus connect?

Answer 9

= connects the umbilical vein to inferior vena cava

Question 10

what does the foramen oval represent and what does it connect?

Answer 10

= opening in atrial septum connecting RA to LA

Question 11

what does the ductus arteriosus connect?

Answer 11

= connects pulmonary bifurcation to descending aorta

Question 12

what do the ductus venosus carry and where to?

Answer 12

majority of placental blood straight into IVC bypassing portal circulation

Question 13

what does the foramen oval allow? (2)

Answer 13

1) allows blood flow from right to left atrium

2) allows best oxygenated blood toe enter left atrium then onto LV, ascending aorta, carotids

Question 14

what is there on the left atrium side?

Answer 14

membrane flap

Question 15

what percentage of RV output goes to lungs?

where does the rest of the RV output go?

Answer 15

only 7%

= rest goes via ductus arteriosus to join descending aorta

Question 16

how is patency of ductus arteriosus maintained?

Answer 16

= by circulating prostaglandins E2 produced by placenta

Question 17

what adaptations happen minutes following birth?

Answer 17

1) baby inflates lungs & cries
2) goes from blue to pink
3) cord clamped and cut

Question 18

how is pulmonary vascular resistance (PVR) decreased in the foetus?

Answer 18

• breath in = lungs expand

- increased circulating oxygen

Question 19

how is systemic vascular resistance (SVR) increased in the foetus?

Answer 19

• cord clamped and cut

Question 20

as PVR falls and SVR rises what happens;

1) to the LA pressure compared to RA pressure?
2) to the flap?

Answer 20

1) LA pressure exceeds RA pressure

2) flap is pushed closed

Question 21

what happens within the first few hours and days to the ductus arteriosus?

Answer 21

= closes due to construction

Within hours to days;
- functional closure

Within 7-10 days
- anatomical closure

Question 22

what does the ductus arteriosus end up as?

Answer 22

= fibrous ligament

e.g. ligamentum arteriosum

Question 23

in what situation is it most common to develop failure of duct closure?

Answer 23

= in premature babies

Question 24

what are the treatment options for failure of duct closure?

Answer 24

= wait and see
= NSAIDS
= surgery

Question 25

what do some congenital heart diseases cause?

Answer 25

= duct dependent circulation

Question 26

what can be used to keep the duct open?

Answer 26

= IV prostaglandin E2 until an alternative shunt is established or definitive surgery carried out.

Question 27

when does pulmonary resistance reach normal adults type levels?

Answer 27

= by 2-3months

Question 28

when is the failure of adaptation in foetus most likely to happen?

Answer 28

= in sick babies

1) sepsis
2) hypoxic ischaemic insult
3) meconium aspiration syndrome
4) cold stress

Question 29

what can failure of adaptation be related to?

Answer 29

= underlying anatomical abnormality

e.g. congenital diaphragmatic hernia

Question 30

what is an example of a problem that could happen as a result of failure to adapt?

Answer 30

= persistent pulmonary hypertension of newborn

Question 31

what happens to lung vascular resistance, shunts and babies colour in persistent pulmonary hypertension of newborn (PPHN)?

Answer 31

Lung vascular resistance
= fails to fall

Shunts remain
= right to left flow at PFO
= right to left flow at PDA

Baby
= blue

Question 32

In PPHN, describe the pre and post ductal oxygen saturation?

Answer 32

there is a large difference.

Question 33

how would you treat PPHN?

Answer 33

• ventilation
• oxygenation
• maintain high systemic blood pressure
• inhaled nitric oxide
• ECLS

Question 34

how would you reduce PVR?

Answer 34

• oxygen
• ventilation
• sedation
• thermo-regulation
• correction of acidosis
• treatment of sepsis
• inhaled nitric oxide

Question 35

how would you increased SYV

Answer 35

• maintain higher than adequate BP
• inotropes
• support other organ function
• in severe cases extra corporeal life supply