Session 9 - Fetal Growth and Development Flashcards
During which weeks are the pre-embryonic, embryonic, and fetal periods?
pre-embryonic - up to 3 weeks
embryonic - 3 to 8 weeks
fetal - 9 to 38 weeks
How does crown rump length change during pregnancy?
Increases rapidly until early fetal periods.
At what week is the head approx half of the crown rump length?
9
What is the proportion of the body to the head at healthy birth?
head is 1/4 of body
At what stage and week is the resp system specialised
In fetal period after 24 weeks
What are the 4 stages of development of the resp system? Name their time periods
- Pseudoglandular: 8 to 16 weeks
- Canalicular stage: 16 to 26 weeks
- Terminal Sac stage: 26 week to term
- Aleolar period: late fetal to 8 years
What occurs in the pseudoglandular stage?
- Duct system forms within the bronchopulmonary segments
- Bronchioles develop
What occurs in the canalicular stage?
- Forming of resp bronchioles
- More vascular
- May be viable
What occurs in the terminal sac stage?
- Terminal sacs bud from resp bronchioles
- Primitive alveoli
- Differentiation of pneumocytes to form type 1 (gas exchange) and type 2 (surfactant production)
How are the lungs prepared before birth?
- Breathing movement - conditioning of resp musculature
- Fluid filled - helps development
What is the function of corticospinal tracts? WHen do they start to form?
Required for coordinated voluntary movement. Begin to form in 4th month
When does myelination of the spinal cord and the brain begin?
Spinal cord - 20th week
Brain - 36 week
After what week does the fetus begin to move?
week 8
What changes occur to the brain during the fetal period?
- Differentiation of cerebrum and cerebellum
- Formation of gyri and sulci as brain grows faster than head
- Formaton and myelination of nuclei and tracts
At what week is the mother made aware of fetal movement?
week 17+
When is the definitive fetal heart rate achieved?
After 15 weeks
At what week is the renal pelvis and calcyes present?
23
What is the major constituent of amniotic fluid?
urine
How can fetal development be assessed?
USS
Non stress tests
Measuring biophysical profiles
What are the 5 factors measured in biophysical profiles? What does each test?
- Fetal movement - nervous, MSK
- Fetal tone - nervous, MSK
- Fetal breathing - Resp, MSK, nervous
- Amniotic fluid volume - Urinary, GI
- Fetal Heart Rate - Resp
What causes asymmetrical growth restriction?
Occurs with deprivation of nutritional and oxygen supply to the fetus
How can the duration of pregnancy be measured?
- Fertilisation age
- Age since mothers last menstrual period
What are criteria that can be used to estimate fetal age? What measurements are specific to T1 and T2/3
- Foot length
- Weight after delivery
- Appearance after delivery
T1 - crown rump length
T2/3 - biparietal diameter of head
What is oligohydramnios? What can it cause?
- Too little amniotic fluid
- Can cause placental insufficency, fetal renal impairment, pre-eclampsia
