9. Fetal Growth And Development Flashcards
What happens generally in the embryonic period?
Organogenetic period - organs formed
Absolute growth is very small
When does CRL (crown-rump length) increase rapidly?
Pre-embryonic
Embryonic
Early fetal periods
Why is weight gain slow at first?
Embryo - intense morphogenesis and differentiation, little weight gain, placental growth most significant
Early fetus - protein deposition
Late fetus - adipose deposition
How is fetal wellbeing monitored?
Mother - fetal movements
Regular measurements of uterine expansion - symphysis-fundal height
Ultrasound scan
Why is USS used in pregnancy?
Safe
Can be used early in pregnancy to calculate age (and rule out ectopic/number of fetuses)
Routinely carried out at 20 weeks - asses fetal growth, fetal anomalies
How is fetal age estimated?
Last menstrual period - prone to inaccuracy
Developmental criteria
When is the crown-rump length measured?
Between 7 and 13 weeks to date the pregnancy and estimated EDD
What is the biparietal diameter?
Distance between the parietal bones of the fetal skull
Used in combination with abdominal circumference and femur length for dating and growth monitoring
Useful for anomaly detection
What are the classifications for birth weights?
3500g is average
<2500g suggests growth restriction
>4500g is macrosomia
Why can babies have low birth-weight?
Premature
Constitutionally small
Suffering growth restriction - associated with neonatal morbidity and mortality
What part of the respiratory system is formed in embryonic stage?
Bronchopulmonary tree
When does functional specialisation of the respiratory system occur?
Fetal period
What does the respiratory system develop from?
Primitive gut tube
Respiratory diverticulum comes off tube
Tracheoesophageal septum forms to separate trachea and oesophagus
What happens in the pseudoglandular stage (weeks 8-16)?
Duct system begins to form within the bronchopulmonary segments created during the embryonic period - bronchioles
What happens in the canalicular stage (weeks 16-26)?
Formation of respiratory bronchioles - budding from bronchioles formed during the pseudoglandular stage
What happens in the terminal sac stage (weeks 26)?
Terminal sacs begin to bud from respiratory bronchioles
Differentiation of type I and type II pneumocytes - surfactant to minimise surface tension
Why does the fetus make breathing movements?
Conditioning of respiratory musculature ready for birth
Ensures amniotic fluid moves into the lungs which is crucial for normal lung development
When is the threshold of viability?
Only a possibility once the lungs have entered the terminal sac stage of development
>24 weeks
What is respiratory distress syndrome?
Often affects infants born prematurely
Insufficient surfactant production
What should be done if pre-term delivery is unavoidable or inevitable?
Glucocorticoid treatment of mother
Increases surfactant production in fetus
When is the definitive fetal heart rate achieved?
Around 15 weeks
When does fetal kidney function begin?
Week 10
Is fetal kidney function necessary for survival in utero?
No, but without it there is oligohydramnios
What can cause oligohydramnios?
Placental insufficiency
Fetal renal impairment
What can cause polyhydramnios?
Fetal abnormality - e.g. inability to swallow
When do corticospinal tracts required for coordinated voluntary movements begin to form?
4th month
When does myelination of brain begin?
In 9th month
When does movement of fetus start?
8th week
What is quickening?
Maternal awareness of fetal movements from 15-17 weeks onwards
