Repro 9 Flashcards
What would happen if foetal blood passed through the liver and mix with venous blood from the body ?
It would lose most of its oxygen
What are the 4 most important systems to determine survival outside the uterus?
Nervous system
Cardiovascular
Respiratory
Urinary
In the period up until the foetal period, what is the most important structure and what amount of weight does the foetus gain?
The placenta is the most important thing. It’s needed to ensure there is a healthy pregnancy. There is not much weight gained by the embryo at this point.
When does the ‘organogenetic’ period occur ?
This occurs in the embryonic period, week 3-8.
What is the crown rump length and CRL would you expect of a foetus at:
- 9 weeks
- 12 weeks
- 20 weeks
- 26 weeks
- 38 weeks
5cm 8.5cm 19cm 28cm 36cm
What structure of the foetus makes up approximately half of the CRL at around week 9?
The head, as brain development is imperative.
In a lady who is expecting her first child, at approximately what week would you expect her to feel foetal movements?
Week 20.
How is uterine expansion measured?
This is a regular measurement.
It’s measure by the symphysis-fundal height.
It’s measured from the top of the palpable uterus to the superior edge of the pubic symphysis.
Define the foetal period
Pre embryonic period - 3 weeks
Embryonic period - 3-8 weeks
Foetal period - 8 weeks to term.
What is the symphsis-fundal height
A measure from the top of the palpable uterus to the superior edge of the pubic symphysis.
What is USS and what are its key features.
UltraSoundScan
- safe
- can detect ectopic pregnancy and the number of foetuses
- routinely carried out
- assesses foetal growth and anomalies
At which week is the USS routinely carried out?
At week 20.
When estimating foetal age, why is the last menstrual period not always the best idea?
It’s prone to inaccuracies.
When is the CRL measured and what information does this give us?
It’s done between week 7-13 and it dates the pregnancy as well as giving us the estimated due date.
Is CRL measurement used in all trimester? If so explain its use in later stages. If not, which trimester (s) is it not used in?
Not used in trimester 2 or 3.
What is the bi parietal diameter?
This distance between the parietal bones of the skull.
What is AC and FL and with which measurement are they used for dating and growth monitoring ?
Abdominal circumference and femur length
Used with bi parietal diameter to date and growth monitoring.
What is the average weight of a baby at birth and what is considered macrosomia and give one risk factor for such a baby.
3500g is considered average.
4500g is considered macrosomia and maternal diabetes is considered a risk factor for this.
Describe the 3 stages in the development of the respiratory system.
- Respiratory diverticulum appears as an outgrowth from the future oesphagous
- tracheoesphageal septum appears between the future trachea and oesphagous.
- separate structures appear - the oesphagous and trachea.
In terms of respiratory development, what is the name of the stage at weeks 8-16 and what is the epithelium that develops? Mention viability.
This is the pseudoglandular stage.
Duct systems begin to form within the bronchopulmonary tree.
No air sacs. The ducts are lined with columnar epithelium.
NOT VIABLE.
Discuss the stage in respiratory development from week 16-26. Viable?
This is the canalicular stage.
Respiratory bronchioles form from buds that were present in the pseudoglandular stage.
Still not suitable for gas exchange.
More terminal sacs, and towards the end of this period, the foetus may be viable.
What is the stage in respiratory development from week 26 - term? Is this viable?
This is the terminal sac stage.
Terminal sacs begin to bud from the respiratory bronchioles.
Differentiation of type I and II pneumocytes.
What epithelium are type I and II made from, and what are their duties?
Type I - simple squamous - one cell thick -gaseous exchange.
Type II - simple cuboidal - secrete surfactant.
What is respiratory distress syndrome if ore term delivery is unavoidable or inevitable, what treatment option is there?
This is when there is inadequate surfactant production by the foetus.
If the baby must be delivered for whatever reason, glucocorticoid treatment OF THE MOTHER can be commenced, which increases surfactant production of the foetus.
What is foetal bradycardia associated with?
Foetal demise.
What is oligohydramnios and how does it occur?
This is a reduction in amniotic fluid volume.
Normally occurs when foetal kidney function is compromised. Foetal kidney function is not necessary for in vivo survival however it’s essential to amniotic fluid volume.
Why is the volume of the amniotic fluid so important?
It’s an indication of problems.
Eg
- oligohydramnios could be due to placental insufficiency or foetal kidney compromise.
- polyhydramnios (too much) could be due to problems with foetal swallowing.
Briefly outline nervous system development in the foetus.
- First to begin developing and the last to finish.
- Corticospinal tracts required for voluntary movement only begin to develop from the 4th month.
- myelination of the brain only begins in the 9th month
- which is why you see increasing repertoire of movements within first year.
What is “quickening” and why is it important?
This is when the mother becomes aware of the foetal movements.
Usually occurs around week 17
Low cost and simple method of ante natal surveillance.
Allows assessment of which foetuses need to be followed up.
Describe in outline the techniques used to assessment foetal development.
USS CRL Amniotic fluid volume Symphysis-fundal height Bi parietal diameter.
Describe two adaptations to foetal blood that enable oxygen content of foetal blood to increase.
It has different haemoglobin - HbF
- foetal pO2 is 4kPa at best - this would = 45% sats in adults - no go.
- 4kPa = 70% sats in foetus due to altered HbF.
It has more Hb - the alpha subunits alter the shape of the molecule which increase its affinity for oxygen.
- this increases the amount of foetal haemoglobin.
What is the Hb level in adults and foetal blood?
12-14 g/DL in adults
18-20 g/DL in foetus.
Why does the foetus have a relatively normal pCO2?
Under the action of progesterone, the mother hyperventilates and breathes off the extra CO2.
However this can cause respiratory alkalosis - can you think how the maternal body responds?
What does surfactant do, in relation to respiration? Where is it produced.
By the type II pneumocytes.
It lowers the surface tension so that inspiration occurs with least effort.
Through which vessel does the foetal bloody shunt around the liver?
Ductus venosus.
When the oxygenated blood in the umbilical vein mixes with the blood in the inferior vena cava, why is this not much of a problem.
The foetus is only small and its lower body is not very metabolically active and so there is not much loss of oxygen.
How is the mixing of oxygenated blood with blood from the descending vena cava prevented in the right atrium?
Superior vena cava has deoxygenated blood from the face and brain.
It doesn’t mix with blood arriving in the right atrium arriving from the inferior vena cava by Crista Dividens.
- this shunts the blood from inferior vena cava through foramen ovale into the left atrium, by passing the pulmonary circulation.
Why does deoxygenated blood from the brain largely bypass the lungs even though it’s pumped out from the right ventricle?
Foetal lungs collapsed = increase pulmonary resistance.
- pulmonary artery pressure is therefore high due to pulmonary resistance.
- pulmonary artery and the aorta are connected to each other via shunt
- ductus arteriosus.
- pulmonary artery pressure»_space; aorta
- blood flows out of pulmonary artery through ductus arteriosus into aorta - due to higher pressure.
Where does the ductus arteriosus connect the pulmonary artery with the aorta.
What does this ensure for the blood to the brain?
Attaches distal to the branch to the head.
This ensures that the blood going to the brain is oxygenated
- this will be from the left ventricle through the aorta.
- there is not a lot of venous return to left artery from lungs
- ensures the blood going from the left ventricle is oxygenated.
What does the way the foetal circulation is set up, depend on?
- pulmonary resistance
- PDA
- pulmonary artery pressure»_space; aorta
- liver bypass
- PDV
- RA pressure»_space; LA pressure
- foramen ovale.
What makes the ductus arteriosus contract?
It is sensitive to high pO2
- baby takes first breath
- pulmonary resistance decreases
- more oxygenation occurring as blood goes through lungs
- smooth muscle in walls of ductus arteriosus contract due to pO2.
What is hypoxic pulmonary vasoconstriction?
In the presence of hypoxia, pulmonary arteries constrict to divert blood to alveoli with a high oxygen saturation.
- the redistribution of the blood to well ventilated areas with higher oxygen increases the total area involved in gaseous exchange.
- increases the ventilation:perfusion ratio.
Why is the amniotic fluid useful diagnostically to us, and helpful to the foetus?
To the foetus:
- keeps it hydrated
- shock absorber
To us:
- amniocentesis
- contains cells from the foetus itself so therefore we can analyse them.
What volume of amniotic fluid would you expect to see at 40 weeks of pregnancy?
500ml
At 38 weeks, what volume of amniotic fluid is expected?
1L
What is meconium?
When the foetus drinks the amniotic fluid, it filters it. It then urinates it out - 100ml. This is hypotonic.
The part that is filtered out is debris and this is known as meconium.
Why are some babies put under UV light
This stimulates them to conjugate bilirubin
What doesn’t foetal Hb bind 2,3 BPG
This binds to Beta subunit in the adult but the foetus doesn’t have betas units so it can’t bind 2,3 BPG.
How does the foramen ovale close.
Upon the first few breaths, the pressure increases in the left atrium above that of the right atrium which closes the foramen.
