Flashcards in Repro 9.2 Fetal growth and development. Deck (46):
What is the main function of the embryonic period?
To lay the foundations for the future systems of the body.
At this point though, they are immature.
What is the main function of the fetal period?
The growth and maturation of the systems and structures created in the embryonic period.
Prepares the fetus for life after birth,
How long does the fetal period last?
What patterns of growth occur during the embryonic period?
-organogenetic period (large growth and activity)
-absolute growth is very small
-weight gain is small
-placental growth of most significance
what patterns of growth occur in the fetal period?
Both growth and weight gain accelerate.
early fetus- protein deposition (for muscle growth, results in a lot of weight gain)
late fetus- adipose deposition (for regulation of body temperature)
What is CRL?
Crown- rump length.
When is CRL most significant?
increases rapidly during the preembryonic, embryonic and early fetal periods.
most signifcant in early fetal period, until around 20 weeks when it is visible
With regards to body proportions, what is seen at arounf week 9?
The head is half of the crown-rump length
At birth, approximately what proportion of the neonates length is made up by the head?
Ante-natally, how can you assess fetal well-being?
-asking the mother (she will be aware of what is 'normal' for that child and can report any changes)
-Measurements of uterine expansion by palpating for the sympehsis-fundal height.
Why is the USS the investigation of choice and what is it used for?
It is SAFE for the fetus, no radiation is involved,
-can be used in early pregnancy to etimate age
-can be used to look for any fetal abnormalities
When is an USS routinely carried out?
Why at this time?
At around 20 weeks.
By this point all systems are present so the doctor can make an assessment.
What are some methods of estimating fetal age?
-last menstrual period
-devleopmental criteria (using USS)
-abdomen circumference and femur length
Why is using the LMP to estimate the fetal age not that good?
-prone to innaccuracys (women aren't always regular, there may be a small amount of breakthrough bleeding during implantation at around day 14 which can lead to some confusion.
When is the best time to use CRL to estimate fetal age?
Between weeks 7 and 13.
What is the first antenatal scan in pregnancy used to look for?
-CRL to estimate the age of the neonate and EDD
-to check for the number of embryos
-to check for ectopic pregnancys
-check for viability (heart beat present, is it bradycardic?)
What is the bi-parietal diameter and how is it used?
The space between the 2 parietal bones of the fetal skull,
used alongside abdominal circumference and femur length to date age of fetus in the late fetal period.
What is the use of 3/4D USS?
-shows the fetus in real time, so can see suckling, or breathing etc
-used as a complimentary tool to standard USS
-nice for the parents to have
What is classified as an average birth weight?
What is classified as a macrosomic fetus?
What is classified as a very small fetus, and what might this indicate?
<2500, growth restriction.
What factors can lead to a low birth weight?
-constitutionally small (small mothers have small babies)
What are some complications associated with a macrosomic fetus?
What can lead to a growth restriction?
-infections eg rubella
-smoking, alcohol, drug use
With regards to lung development, what happens during the emrbyonic period??
Production of the broncho-pulmonary tree
With regards to lung development, what happens during weeks 8-16?
Duct system forming from the broncho-pulmonary tree developed in the embryonic period.
Formation of bronchioles.
With regards to lung development, what happens during weeks 16-26?
Respiratory bronchioles are formed.
These bud off the bronchioles formes in the pseudoglandular stage.
With regards to lung development, what happens from week 26- term?
Terminal sac stage
Terminal sac develop from respiratory bronchioles.
Type 1 and 2 pneumocytes differentiate and you get formation of surfactant (Although only a small amount is produced until around weeks 36)
What are the stages of lung development during the fetal period?
-pseudoglandular stage (weeks 8-16)
-canalicular stage (weeks 16-26)
-teminal sac stage (weeks 26-term)
What is the function of practice breathing movements?
Draw amniotic fluid into the lungs which is crucial for lung development
conditioning of the respiratory musculature, preparing it for life after birth
Where does the respiratory system initially develop from?
an out-pouching of the oesophagus, of the GI tract.
What is meant by threshold of viability?
The point at which a fetus is deemed as viable and able to survive out of the uterus.
Only possible once the lungs have entered the terminal sac stage of development (Currently set at 24 weeks, but mortality is still very high)
Can't keep being pushed back because there is a limit where the lungs wont be mature enough to cope.
What is infant respiratory distress syndrome?
Often happens to pre-term neonates because they haven't produced sufficient surfactant (happens in the last few weeks of gestation)
Neonate has difficulty breathing because it can't inflate its lungs easily, and cannot get enough oxygen so will become hypoxic eventually.
In what cases can you predict IRDS and what would you do in these cases?
When a mother has a condition which means shes going to need to deliver prematurely, eg pre-eclampsia, or multiple children.
Give the mother glucocorticoid treatment, this increases surfactant production of the fetus.
When should the fetal heart rate be established and what should it be?
By week 15, it should be between 110-150 bpm.
When should you be worried about fetal heart rate?
If it is bradycardic, so below 110, as this can suggest a placental insufficiency, hypoxia of the fetus, and is associated with fetal death.
What is the function of the fetal kidney?
-Doesn't function as an adult kidney but does produce most of the amniotic fluid.
What condition will occur without functioning fetal kidneys?
Oligohydroamnios- reduction in amniotic volume
What are some major causes of oligohydroamnios?
-placental insufficiency (initially the placental membranes produce amniotic fluid)
-renal impairment (major contributor to volume of amniotic fluid)
What is polyhydroamnios?
Too much amniotic fluid
What could be a cause of polyhydroamnios?
Inability of the fetus to swallow, (usually swallows it and recycles).
When do voluntary movements occur in utero and what allows this to happen?
corticospinal tracts are formed, and this happens at around 4 months.
Why, when the fetus is born, can it not walk, or do all the movements adults can do?
Corticospinal tracts are not fully myelinated.
This only begins in the 9th month and continues into early neonatal life, as seen by the increased mobility of the neonate.
When does the fetus first begin to move?
Around week 8
What movements does the fetus do in utero?