Repro 9 Flashcards
How is O2 exchanged at the placenta?
Gradient of PPs produced, maternal pO2 increases slightly, foetal pO2 low
Why is it difficult to maintain a low foetal pO2?
Hint: 2 reasons
Foetal haemoglobin variant increases pO2
Foetal haematocrit higher than in adults
What else promotes O2 exchange to foetus?
Increased production of maternal 2,3 DPG
Double Bohr effect
Foetal haemoglobin
What makes foetal haemoglobin good for O2 exchange from mother?
2 alpha 2 gamma sub units
Doesn’t bind 2,3 DPG as well as HbA
What is the double Bohr effect?
CO2 passes into intervillous blood -> pH decreases -> 1st effect
Hb O2 affinity decreases -> But CO2 also lost -> pH rises -> 2nd effect -> O2 affinity increases
What is the double Haldane effect?
As Hb gives up O2 it can accept more CO2, foetal Hb exchanges them so local pCO2 doesn’t alter
How many foetal circulatory shunts are there? Now name them and the organ they bypass
3 - Dutus venosus (liver) Foramen ovale (R ventricle and lungs) Ductus arteriosus (lungs)
Why is the ductus venosus needed?
Connects umbilical vein to IVC
Bypasses the liver
Why is the foramen ovale needed?
R atrial pressure higher than L, blood R->L (as lungs not functional!)
Why is the ductus arteriousus needed?
RV -> PT
Minimises drop in O2 saturation
What does the foetus do in response to hypoxia?
Increases [Hbf]
Redistributes blood flow
Foetal HR slows (vagal stimulation)
If chronic; growth restriction, behavioural changes etc.
Which hormones are needed for foetal growth?
Insulin Insulin-like growth factor I&II Leptin (from placenta) Epidermal growth factor Transforming growth factor alpha
Describe amniotic fluid
Fluid in amniotic sac
Protects foetus
Contributes to lung development
Apporx. 1litre max
How is amniotic fluid recycled?
Foetal urinary tract from produces urine from wk9, up to 800ml/day
Foetal lungs and GIT also involved
What is the composition of amniotic fluid?
98% water
electrolytes, creatinine, urea, bile pigments, renin, glucose, hormones, foetal cells etc.
What is amniocentesis?
sampling of amniotic fluid with needle and syringe for foetal cell collection (used in e.g. karyotyping)
What condition is physiologically common in the foetus due to immaturity of organs?
Jaundice, placenta clears bilirubin as foetus cannot
Boradly deifne the foetal period
The time involving the growth and physiological maturation of the structures creathed during the embryonic period i.e the preparation for independent life
What are the differential stages of growth of a conceptus?
Pre-embryonic (1st 2wks)
Embryonic (wks 3-8)
Foetal (wks9-38)
What differentiates the stages of development of a conceptus?
Embryonic = intense activity but little absolute growth
Early foetal = protein deposition
Late foetal = adipose deposition
What is CRL?
Crown Rump Length - increases rapidly in pre-embryonic and embryonic periods, used to estimate EDD
How is foetal well-being assessed ante-natally?
Foetal movements
Regular measurements of uterine expansion (symphysis-fundal height)
USS
What use does an obstetric USS have?
It is safe Used in age calculation Can rule out ectopic Assess foetal growth Can identify other anomalies
What two ways are used to estimate foetal age?
LMP (inaccurate)
Developmental criteria
