17 - Fetal Growth and Development Flashcards
What is the fetal period?
- 9 weeks to term
- Lots of weight gain and growth and the fetus gets bigger than placenta
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What is crown rump length?
Length of fetus from head to tail, used mainly in early pregnancy as increases dramatically
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In the different periods of embryonic growth, what tissue contributes most to the weight of the fetus?
- Early fetal: protein due to muscle development
- Late fetal: adipose for metabolic purposes and heat regulation
What are the body proportions of the fetus as it moves through each period?
At first the head is 50% of the length of the fetus, but goes to 25% by birth
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What are the different ways that we can assess fetal wellbeing?
- Ask mother about fetal movements around 20 weeks
- Symphis fundal height is non invasive
- Ultrasound scan
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How do we measure symphysis fundal height and why may it not correlate to weeks of gestation?
- After 20 weeks the week of the pregnancy should roughly equal the number of cm measurement e.g 28cm at 28 weeks
- May not correlate as may be oligohydraminos, IUGR, fetal head dropping into pelvis, polyhydraminos from swallowing difficulties or urine production issues
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What can an ultrasound scan be used to image in the fetus?
- Estimate date of pregnancy
- Rule out ectopics
- Identify multiple pregnancies
- Measure fetal growth at 20 weeks and any anomolies
Done at 20 weeks as structures have developed and are big enough to be seen at this point
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How can we estimate fetal age?
- LMP: date of last menstrual period prone to inaccuracy
- Developmental criteria:
CRL: good way to date from 7 to 13 weeks as linear growth
Biparietal Diameter: distance between parietal bones in second and third trimester
Abdominal circumference: used with above in second and third trimester. Often used in conjuction with femur length
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What is the average birth weight of babies?
3500g
- >4500g macrosomia
- <2500g suggest growth restriction
Why may a baby have a low birth weight?
- Premature
- Constitutionally small (e.g mother is small)
- Growth restriction
(high birth weight usually due to gestational diabetes)
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What are the different stages of the development of the respiratory system in the fetus?
- Embryonic period: outpouching of foregut to create bronchopulmonary tree
- Week 8-16: Pseudoglandular stage. Duct system begins to form forming bronchioles
- Week 16 - 26: Canalicular stage where respiratory bronchioles are forming, still no alveoli
- Week 26 - Term: Terminal sacs at the end of respiratory bronchioles. Differentiation of type I and type II pneumocytes so surfactant
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What determines fetal viability and what would you do if you had to deliver a baby before this point?
- Viabity depends if pneumocytes are present or not so when enter terminal sac stage at 24 weeks
- If need to deliver early give mother glucocorticoids to try and stimulate surfactant production
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What is the normal fetal heartbeat and why is it important to know this?
- 110 to 160 bpm
- Fetal bradycardia can mean fetal distress
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/328/162/a_image_thumb.png?1574489993)
What are some causes of oligo and polyhydraminos?
- Urine production starts week 10
- Oligo: renal impairment, placental insufficiency
- Poly: CNS defect, tracheo-oesophageal fistual, inability to swallow
![](https://s3.amazonaws.com/brainscape-prod/system/cm/432/328/170/a_image_thumb.png?1574490160)
How long does the development of the nervous system take?
- First and last
- Corticospinal tracts needed for voluntary movements start to develop in the 4th month
- Myelination of brain and these tracts still occuring after birth up to 1 year so increase in infant mobility
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