Fetal Phsyiology Flashcards
Does fetal blood have a lower or higher pO2 than maternal blood?
Lower, to allow a gradient of transfer from mother to fetus
Progesterone causes hyperventilation in mum-> maternal Respiratory alkalosis.
How is this counteracted?
Increased maternal 2,3 BPG production, reducing Hb’s O2 affinity and promoting release of O2 to fetus
(Hyperventilation maintains a CO2 gradient from fetus to mother)
When is HbF predominant in the baby?
Describe its structure
Why does it have a greater O2 affinity than maternal Hb?
- By week 12
- 2 Alpha and 2 Gamma subunits
- Doesn’t bind 2,3 BPG as effectively as Maternal Hb
Describe the Double Bohr effect on Fetal and Maternal Circulation
Maternal;
- CO2 passes into intervillous blood -> pH decrease
- Decreased O2 affinity in Maternal Hb
Fetal;
- Gives up CO2-> pH Increase
- Increased O2 affinity in HbF
Describe the Double Haldane effect in maternal and Fetal circulation
Maternal;
- As maternal Hb gives up O2, accepts more CO2
Fetal;
- As O2 is accepted, more CO2 is given up
Suggest a possible Fetal response to hypoxia
Bradycardia via vagal stimulation, to reduce O2 demand of heart
(Can be included in the term Fetal Distress)
Smoking can cause chronic Hypoxaemia leading to what fetal condition?
Intrauterine growth restriction
Are lungs function in utero?
No
What veins are connected by the Ducts Venosus?
Umbilical vein to IVC
Carries oxygenated blood from Placenta, bypassing Liver
Why is it important that the liver is bypassed by the Ductus Venosus?
Maintains high level of O2 saturation in blood
What is the Crista Dividens?
What is its function?
A ‘Crest’ formed from the free border of the Septum Secundum
Creates 2 streams of blood flow;
- Majority goes to LA
- Remaining continues to RV
In the Fetus, what 2 organs get the most O2?
Brain and Heart (Coronary arteries)
What hormones are key to Fetal growth?
Insulin-like Growth Factors (IGF 1 and 2)
Describe the normal growth pattern of the fetus during pregnancy
Trimester 1 (Weeks 0-20): Hyperplasia of cells
Trimester 2 (Weeks 20-28): Mix of Hyperplasia and Hypertrophy
Trimester 3 (Week 28 onwards): Mainly Hypertrophy
What are 2 consequences of Maternal Malnutrition?
Nutritional and hormones status during fetal life can also affect health in later life
Symmetrical growth restriction: All parts of fetus are small
Asymmetrical growth restriction: ‘Head sparing’. Restriction on abdomen, but it is disproportionately smaller than head
What are 2 functions of the Amniotic Fluid?
What is the volume proportional to?
- Mechanical protection
- Contains substances critical for lung development
- Fetus size
Describe how Amniotic fluid can be used as an investigation technique
- Contains fetal cells, can be aspirated (Amniocentesis)
- Can be useful for Fetal Karyotyping (E.g Down’s)
Suggest 2 disadvantages of Amniocentesis
- Invasive
- Carries risk of miscarriage
Describe 1 sign of Fetal Distress
Meconium staining/ Meconium stained liquor :
- Mecoinium released prematurely from fetal GI tract
- Inhaled by fetus-> Meconium Aspiration
(Can also occur in pregnancies longer than 40 weeks, which can cause fetal distress)
Describe the production of amniotic fluid
- Essentially composed of Fetal urine
- Production of urine begins around week 9
Describe the composition of Amniotic Fluid
- Mainly water, electrolytes and other substances typically found in urine
- Also contains elements of fetal skin that have been lost during pregnancy
List the 2 mechanisms of recycling amniotic fluid
- Inhalation of fluid by Fetus PRACTICING breathing movements
- Swallowing of Amniotic fluid by Fetus
Inhalation of amniotic fluid by the Fetus contributes to production of what?
Production of lung, especially surfactant
What is Meconium?
When is it first passed out of the GI tract and how?
- Accumulation of debris in the GI tract
- Passed out after delivery as the baby’s first stool
