Week 9.1 - fetal growth and development Flashcards
When is the fetal period?
-9 to 38 weeks
What is the organogenetic period?
-embryonic period characterised by intense activity but small absolute growth
When does CRL increase most rapidly?
-Pre-embryonic,, embryonic and early fetal periods
When does weight gain increase?
-Mid and late fetal period
When does protein and adipose deposition occur?
- Protein in early fetal period
- Adipose in late fetal period
Why can pre-term babies have difficulty maintaining their own body temp?
-Adipose deposition doesnt occur till late fetal period so may be inadequate to control temp
Describe the body proportions just before the fetal period (ie week 9)
-Head is half CRL
State 3 ways ante-natal assessment of fetal well-being can be made
- Fetal movements as felt by mother (quickening)
- Regular measurements of symphysis-fundal height
- Ultrasouns scan
Why is an ultrasound scan used in obstetrics?
- Safe and cheap
- Can be used to calculate age, number of fetuses, rule out ectopic, location of baby etc
- Assess growth and fetal anomalies
How is fetal age estimated?
- Last menstrual period
- Developmental criteria
- CRL in T1
Why is LMP prone to inaccuracy?
- Irregular menstuation
- Implantation bleeding
Why can CRL only be used in T1 to estimate EDD?
-Becomes more unreliable further into pregnancy due to variations in fetus size
What is biparietal diameted? What is it used for?
- Distance between the parietal bones of the fetus
- Used in conjunction with other measurements such as femur length and abdominal diameter to date the pregnancy in T2/3
Describe the average birthweight, growth restriction and macrosomia
- 3500g = average
- 4500g = macrosomia
When in pregnancy does the respiratory system develop and why does this effect pre-term survival?
- Relatively late into the fetal period
- Many babies born pre-term do not have a developed resp system to support life
What part of development regarding the respiratory system occurs in the embryonic period?
-Development of the resp diverticulum, tracheooesophageal septum and separation of GI and resp tract forming the bronchopulmonary tree
What happens regarding the resp system between weeks 8-16 of development?
-Pseudoglandular stage -> Bronchiole formation as there is elaboration of the duct system within the bronchopulmonary tree
What happens between weeks 16-26 regarding the respiratory system during fetal development?
-Canilicular stage -> Formation of resp bronchiole as they bud from the bronchioles formed in the pseudoglandular stage
What happens regarding the respiratory system in weeks 26-term of fetal development?
-Terminal sac stage -> Terminal sacs begin to bud from the resp bronchioles and cells differentiate into T1 and T2 pneumocytes
What drives the differentiation of T1 anf T2 pneumocytes during fetal respiratory development?
-Exposure to amniotic fluid
What is the major significant event which can occur after the differentiation of the pneumocytes in the terminal sacs?
-Production of sufficient surfactant to keep the lungs open after partuition
Why is it vital the lungs undergo breathing movements in utero, even though they do not partake in gas exchange?
-Develop the resp musculature needed to sustain life
Why is it vital the lungs are exposed to amniotic fluid in utero?
-It is crucial for normal lung development
Why is the respiratory system involved in the threshold of viability?
-There is a limit beyond which the lungs will not be sufficiently developed to sustain life (before they have entered the terminal sac stage of development ~24 weeks)
What is respiratory distress syndrome?
-Syndrome which effect pre-term neonates whereby there is insufficient surfactant production to adequately allow sufficient respiration
What pharmacologcal intervention can be given to mothers in order to boost surfactant production if a premature birth is unavoidable?
-Glucocorticoid injection
When is the definitive fetal heart rate achieved?
-~15 weeks
When does fetal kidney function begin?
~week 10
Fetal kindey function is not necessary for survival in utero, however what complication would ensue?
-oligohyrdamnios
Give 2 causes of oligohydramnios
- Placental insufficiency
- Fetal renal impairment
What is oligohydramnios/polyhydramnios?
- Too little amniotic fluid
- Too much amniotic fluid
Name 2 causes of polyhydramnios
- Idiopathic
- Inability to swallow amiotic fluid eg misplaces tracheoesophageal septum
When does the nervous system develop in relation to all the other systems?
-First to begin and last to finish
What are the corticospinal tracts required for and when do they begin to develop?
- Voluntary movement
- 4th month
When does myelination of the brain occur?
-Begins in the 9th month and completes in the year after
What is meant by the baby practicing for natal life?
-At about 8 weeks onwards involuntary sensory and motor systems develop and thus suckling and brething movements begin
What is quickening and how is it used?
- Maternal awaremess of fetal movement from approximately wk 17 onwards
- Low cost simple method of ante-partum fetal surveillance.
Which 2 systems have the greatest impact on pre-term survival?
- Resp
- CNS
