Repro 9

Question 1

How is O2 exchanged at the placenta?

Answer 1

Gradient of PPs produced, maternal pO2 increases slightly, foetal pO2 low

Question 2

Why is it difficult to maintain a low foetal pO2?

Hint: 2 reasons

Answer 2

Foetal haemoglobin variant increases pO2

Foetal haematocrit higher than in adults

Question 3

What else promotes O2 exchange to foetus?

Answer 3

Increased production of maternal 2,3 DPG
Double Bohr effect
Foetal haemoglobin

Question 4

What makes foetal haemoglobin good for O2 exchange from mother?

Answer 4

2 alpha 2 gamma sub units

Doesn’t bind 2,3 DPG as well as HbA

Question 5

What is the double Bohr effect?

Answer 5

CO2 passes into intervillous blood -> pH decreases -> 1st effect
Hb O2 affinity decreases -> But CO2 also lost -> pH rises -> 2nd effect -> O2 affinity increases

Question 6

What is the double Haldane effect?

Answer 6

As Hb gives up O2 it can accept more CO2, foetal Hb exchanges them so local pCO2 doesn’t alter

Question 7

How many foetal circulatory shunts are there? Now name them and the organ they bypass

Answer 7

3 - Dutus venosus (liver)
Foramen ovale (R ventricle and lungs)
Ductus arteriosus (lungs)

Question 8

Why is the ductus venosus needed?

Answer 8

Connects umbilical vein to IVC

Bypasses the liver

Question 9

Why is the foramen ovale needed?

Answer 9

R atrial pressure higher than L, blood R->L (as lungs not functional!)

Question 10

Why is the ductus arteriousus needed?

Answer 10

RV -> PT

Minimises drop in O2 saturation

Question 11

What does the foetus do in response to hypoxia?

Answer 11

Increases [Hbf]
Redistributes blood flow
Foetal HR slows (vagal stimulation)
If chronic; growth restriction, behavioural changes etc.

Question 12

Which hormones are needed for foetal growth?

Answer 12

Insulin 
Insulin-like growth factor I&II
Leptin (from placenta)
Epidermal growth factor 
Transforming growth factor alpha

Question 13

Describe amniotic fluid

Answer 13

Fluid in amniotic sac
Protects foetus
Contributes to lung development
Apporx. 1litre max

Question 14

How is amniotic fluid recycled?

Answer 14

Foetal urinary tract from produces urine from wk9, up to 800ml/day
Foetal lungs and GIT also involved

Question 15

What is the composition of amniotic fluid?

Answer 15

98% water

electrolytes, creatinine, urea, bile pigments, renin, glucose, hormones, foetal cells etc.

Question 16

What is amniocentesis?

Answer 16

sampling of amniotic fluid with needle and syringe for foetal cell collection (used in e.g. karyotyping)

Question 17

What condition is physiologically common in the foetus due to immaturity of organs?

Answer 17

Jaundice, placenta clears bilirubin as foetus cannot

Question 18

Boradly deifne the foetal period

Answer 18

The time involving the growth and physiological maturation of the structures creathed during the embryonic period i.e the preparation for independent life

Question 19

What are the differential stages of growth of a conceptus?

Answer 19

Pre-embryonic (1st 2wks)
Embryonic (wks 3-8)
Foetal (wks9-38)

Question 20

What differentiates the stages of development of a conceptus?

Answer 20

Embryonic = intense activity but little absolute growth
Early foetal = protein deposition
Late foetal = adipose deposition

Question 21

What is CRL?

Answer 21

Crown Rump Length - increases rapidly in pre-embryonic and embryonic periods, used to estimate EDD

Question 22

How is foetal well-being assessed ante-natally?

Answer 22

Foetal movements
Regular measurements of uterine expansion (symphysis-fundal height)
USS

Question 23

What use does an obstetric USS have?

Answer 23

It is safe
Used in age calculation 
Can rule out ectopic
Assess foetal growth
Can identify other anomalies

Question 24

What two ways are used to estimate foetal age?

Answer 24

LMP (inaccurate)

Developmental criteria

Question 25

What is the biparietal diameter?

Answer 25

Distance between parietal bones of foetal skull - used with other measurements to date pregnancies

Question 26

What are some other dvelopmental criteria used in dating?

Answer 26

Abdominal circumference

Femur length

Question 27

How is birth-weight classified?

Answer 27

3.5kg average
<2.5kg suggests growth restriction
>4.5kg = macrosomia

Question 28

Why is it important to accurately date pregnanices?

Answer 28

To help discern the casue of low birth-weight i.e. rule out prematurity

Question 29

Which components of the respiratory system develop in the embryonic period?

Answer 29

Bronchopulmonary tree

Question 30

How does the bronchopulmonary tree begin to form?

Answer 30

Buds off gut tube as diverticulum to be separated by tracheoesophageal septum

Question 31

What is the pseudoglandular stage of respiratory system development?

Answer 31

Wks8-16; duct system forms in tree, bronchioles created

Question 32

What is the canalicular stage of respiratory system development?

Answer 32

Wks 16-12; continued formation of respiratory bronchioles as the bud off original ones

Question 33

What is the termianl sac stage of respiratory system development?

Answer 33

Wks26-term; terminal sacs begin to bud from respiratory bronchioles, type I&II pneumocytes differentiate (surfactant)

Question 34

What are the implications of respiratory development on pre-term survival?

Answer 34

Viable only after lungs enter terminal sac stage i.e. >24wks

Question 35

What is respiratory distress syndrome?

Answer 35

Insufficient surfactant production often in premature births

Question 36

What can be done to prevent RDS in cases of unavoidable pre-term delivery?

Answer 36

Glucocorticoid treatment for mother increases surfactant production in foetus

Question 37

What is oligohydramnios?

Answer 37

Deficiency of amniotic fluid, can occur if kidney function doesn’t begin at week 10 as usual

Question 38

What, then, is polyhydramnios?

Answer 38

Too much amniotic fluid volume - can lead to inability to swallow

Question 39

What is quickening?

Answer 39

Maternal awareness of foetal movements (17wks onwards)