17 - Fetal Growth and Development Flashcards

1
Q

What is the fetal period?

A
  • 9 weeks to term
  • Lots of weight gain and growth and the fetus gets bigger than placenta
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2
Q

What is crown rump length?

A

Length of fetus from head to tail, used mainly in early pregnancy as increases dramatically

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3
Q

In the different periods of embryonic growth, what tissue contributes most to the weight of the fetus?

A

- Early fetal: protein due to muscle development

- Late fetal: adipose for metabolic purposes and heat regulation

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4
Q

What are the body proportions of the fetus as it moves through each period?

A

At first the head is 50% of the length of the fetus, but goes to 25% by birth

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5
Q

What are the different ways that we can assess fetal wellbeing?

A
  • Ask mother about fetal movements around 20 weeks

- Symphis fundal height is non invasive

- Ultrasound scan

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6
Q

How do we measure symphysis fundal height and why may it not correlate to weeks of gestation?

A
  • 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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7
Q

What can an ultrasound scan be used to image in the fetus?

A
  • 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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8
Q

How can we estimate fetal age?

A

- 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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9
Q

What is the average birth weight of babies?

A

3500g

  • >4500g macrosomia
  • <2500g suggest growth restriction
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10
Q

Why may a baby have a low birth weight?

A
  • Premature
  • Constitutionally small (e.g mother is small)
  • Growth restriction

(high birth weight usually due to gestational diabetes)

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11
Q

What are the different stages of the development of the respiratory system in the fetus?

A

- 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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12
Q

What determines fetal viability and what would you do if you had to deliver a baby before this point?

A
  • 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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13
Q

What is the normal fetal heartbeat and why is it important to know this?

A
  • 110 to 160 bpm
  • Fetal bradycardia can mean fetal distress
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14
Q

What are some causes of oligo and polyhydraminos?

A
  • Urine production starts week 10
  • Oligo: renal impairment, placental insufficiency

- Poly: CNS defect, tracheo-oesophageal fistual, inability to swallow

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15
Q

How long does the development of the nervous system take?

A
  • 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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16
Q

Why and when do babies start moving in utero?

A
  • Need to practice for independent life after birth, e.g suckling thumb
  • Mother feels quickening around 17 weeks but first movement is probably around 8 weeks
17
Q

As the gravid uterus rests on the pelvic brim it may compress the ureters, what issues can this cause?

A
  • Hydronephrosis
  • Kidney stones
  • Prone to UTIs as stasis
18
Q

What hormone causes a change in maternal carbohydrate metabolism?

A
  • human placental lactogen
  • increases insulin resistance
19
Q

What are some complications of poorly controlled gestational diabetes?

A
  • Preeclampsia
  • Risk of type II DM in baby and mother
  • Still birth
  • Jaundice
  • Hypoglycemia at birth
20
Q

What signs and symptoms suggest pre-eclampsia is worsening in severity?

A
  • Examine optic fundi for cerebral oedema
  • Examine tendon reflexes for hyperreflexaemia
21
Q

What is normal fetal pO2?

A

4kPa

22
Q

What prenatal diagnostic test has the highest risk of pregnancy loss?

A

Chorionic villus sampling

23
Q

What does symmetrical intrauterine growth restriction (both the head circumference and abdominal circumference are lower than normal) suggest?

A