19) Fetal Growth and Development Flashcards
When is the fetal period?
9-38 weeks
What happens in the fetal period (generally)?
Growth and physiological maturation of structures created during embryonic period
What causes rapid weight gain in later fetal period?
Adipose deposition
Describe the changes to crown-rump length during development:
Increases rapidly in pre-embryonic, embryonic and early fetal periods, especially head
After 9 weeks, body and limb growth accelerate
How can fetal age be assessed?
LMP
Developmental criteria
CRL
Biparietal diameter
What is the normal birth weight?
3500g
What birth weight would indicate a growth restriction?
<2500g
What birth weight would indicate macrosomia?
> 4500g
What are some causes of low birth weight?
Premature birth
Constitutionally small
Growth restriction
How can fetal well-being be assessed?
Fetal movements
Symphysis-fundal height
Ultrasound scan
What are the stages of lung development?
Pseudoglandular
Canalicular
Terminal sac
What is the pseudoglandular stage of lung development and when does it occur?
8-16 weeks - terminal bronchioles form in bronchopulmonary segments
What is the canalicular stage of lung development and when does it occur?
16-26 weeks - formation of respiratory bronchioles
What is the terminal sac stage of lung development and when does it occur?
26 weeks to term - terminal sacs bud from resp. bronchioles and differentiation of type 1 and 2 pneumocytes
When do breathing movements take place and why are they need?
12-14 weeks
Conditioning of respiratory musculature
When is viability achieved?
Once lungs have entered terminal sac stage and surfactant is being produced
Describe surfactant production in fetus:
Produced from around 20 weeks but significant increase after 30 weeks
If pre-term delivery is inevitable what treatment is given and why?
Glucocorticoids to mother which drives surfactant production in fetus
When is definitive fetal heart rate achieved?
15 weeks
When does fetal kidney function begin?
10 weeks
What cause oligohydraminos?
Placental insufficiency, fetal renal impairment
What causes polyhydraminos?
Fetal abnormality e.g. inability to swallow
Idiopathic
Why does infant mobility increase in the first year?
Corticospinal tract myelination incomplete at birth
When do fetal movements start and when are they felt by mother?
8th week, felt at 17 weeks
