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15. Reproductive > 9. Foetal Growth and Development > Flashcards

9. Foetal Growth and Development Flashcards

1
Q

When is the foetal period?

A

8 weeks to 38 weeks post fertilisation.

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2
Q

How does crown rump length change through the pre-embryonic, embryonic, and foetal periods?

A

Increases rapidly throughout.

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3
Q

What is deposited in the early and late foetus?

A

Early - protein.

Late - adipose.

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4
Q

How do body proportions change throughout the foetal period?

A

Week 9 - head is half crown rump length.

After that, body length and lower limb length accelerate so by birth, the head makes up 1/4 of crown rump length.

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5
Q

What are the four stages of respiratory system development?

A

Pseudoglandular stage, canalicular stage, terminal sac stage, alveolar period.

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6
Q

How does respiratory system development impact viability?

A

Viability is only possible after 24 weeks due to the late lung development.

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7
Q

Describe the pseudoglandular stage of respiratory system development.

A

Weeks 8-16. Duct system begins to form within bronchopulmonary segments from embryonic period - bronchioles.

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8
Q

Describe the canalicular stage of respiratory system development.

A

Weeks 16-26. Formation of respiratory bronchioles budding from bronchioles form during pseudoglandular stage. Viable towards end of stage as some terminal sacs. More vascular.

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9
Q

Describe the terminal sac stage of respiratory system development.

A

Week 26-term. Terminal sac bud from respiratory bronchioles. Some primitive alveoli. Two types of pneumocytes: i - gas exchange, ii - surfactant from week 20.

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10
Q

Describe the alveolar period of respiratory system development?

A

Late foetal -> 8 years as 95% of alveoli are formed post-natally.

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11
Q

What is the purpose of ‘breathing’ movement in foetal development?

A

Conditioning of the respiratory musculature.

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12
Q

What body system is the first to being development and the last to finished?

A

Nervous system.

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13
Q

What is required for coordinated voluntary movements?

A

Corticospinal tracts.

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14
Q

When does myelination of the brain begin?

A

9th month.

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15
Q

When do movements of the foetus start?

A

Week 8 - development large repertoire of movements practicing for post-natal life.

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16
Q

What becomes the largest part of the brain?

A

Cerebral hemisphere.

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17
Q

Which senses develop first?

A

Hearing and taste before vision.

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18
Q

What is quickening?

A

Foetal movements seen by USS at week 8 but maternal movements from week 17 onwards.

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19
Q

What is foetal bradycardia associated with?

A

Foetal demise.

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20
Q

When if the definitive foetal heart rate achieved?

A

Around 15 weeks.

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21
Q

When does the ascent of the kidneys complete?

A

Week 10.

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22
Q

When does the foetal kidney function begin and what is it called at that point?

A

Week 10, metanephros.

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23
Q

When do renal pelvis and calyces present by?

A

Week 23.

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24
Q

When does histological differentiation of cortex and medulla complete?

A

8 months.

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25
Q

What is the main contribution to amniotic fluid volume?

A

Foetal urine.

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26
Q

What is oligohydramnios indicative of?

A

Poor foetal kidney function.

27
Q

How often does the bladder fill and empty in the foetus?

A

40-60 minutes.

28
Q

What is respiratory distress syndrome?

A

Insufficient surfactant production that often affects infants born prematurely.

29
Q

How is respiratory distress syndrome prevented in unavoidable or inevitable pre-term deliveries?

A

Glucocorticoid treatment of mother to increase surfactant production in the foetus.

30
Q

How can foetal development be assessed?

A

Ultrasound scan, doppler ultrasound, non-stress tests, biophysical profiles, foetal movements kick chart.

31
Q

What is growth restriction defined as in the foetus?

A

Weight below 10th percentile for gestational age.

32
Q

What is symmetrical growth restriction?

A

Growth restriction is generalised and proportional.

33
Q

What is asymmetrical growth restriction?

A

Abdominal growth lags, relative sparing of head growth.

34
Q

When does asymmetrical growth restriction occur?

A

With deprivation of nutritional and oxygen supply to foetus.

35
Q

How can foetal age be estimated?

A

Duration of pregnant - time since last menstrual period; developmental criteria - crown rump length, biparietal diameter of head; symphysis-fundal height.

36
Q

How is duration of pregnancy limited in estimating foetal age?

A

Use of calendar months may cause inaccuracies. Irregular cycles confused time of last menstrual period.

37
Q

What measurements are used in T1 vs T2/3 to measure developmental criteria?

A

T1 - crown-rump length.

T2/3 - biparietal diameter of head.

38
Q

How is the symphysis-fundal height measured?

A

Distance between symphysis pubis to top of uterus (fundus) using a tape measure.

39
Q

What can cause variation in symphysis-fundal measurements?

A

Number of foetuses, volume of amniotic fluid, position of foetus.

40
Q

What is oligohydramnios?

A

Low amniotic fluid volume.

41
Q

What does oligohydramnios suggest?

A

Placental insufficiency, foetal renal imparment, pre-eclampsia.

42
Q

What is polyhydramnios?

A

High amniotic fluid volume.

43
Q

What does polydramnios suggest?

A

Foetal abnormality - inability to swallow, structural problems e.g. blind-ended oesophagus, neurological - unable to coordinate swallowing movements.

44
Q

What are the classifications of birth weight?

A 
<2.5kg = growth restriction
3.5kg = average
>4.5kg = macrosomia
45
Q

What is the effect on foetus of poor nutrition in early pregnancy?

A

Neural tube defects, e.g. DiGeorge syndrome.

46
Q

What is the effect on foetus of poor nutrition in late pregnancy?

A

Asymmetrical growth restriction and subsequent olgihydramnios.

47
Q

What is the foetal circulation before birth?

A

Oxygen blood enters foetus via umbilical vein from placenta, oxygenated blood bypasses liver via ductus venosus, oxygenated blood passes from RA -> LA via foramen ovale, blood passes from pulmonary artery -> aorta via ductus arteriosus, deoxygenated blood returns to placenta via two umbilical arteries.

48
Q

Why is resistance in the foetal lungs high?

A

Hypoxic pulmonary vasoconstriction.

49
Q

What is the circulation of a baby after it’s first breath?

A

Hypoxic pulmonary vasoconstriction is removed so resistance to lungs is reduced. So greater venous return to LA and pressure exceeds that of RA so foramen ovale closes. Constriciton of ductus arteriosus and umbilical artery from decreased prostaglandins and increased O2 saturation of blood. Stasis of blood in umbilical vein and ductus venosus means blood clots and they close.

50
Q

What are the functions of amniotic fluid?

A

Surround foetus for mechanical protection and prevent dehydration by making it a moist environment.

51
Q

How is amniotic fluid turned over in early vs late pregnancy?

A

Early: formed from maternal fluids, foetal extracellular fluid by diffusion across non-keratinised skin.
Later: turnover via foetus.

52
Q

How much urine is made a day at 25 weeks gestation?

A

100ml of hypotonic urine a day.

53
Q

How much urine is made a day by a foetus at term?

A

500ml.

54
Q

What is meconium?

A

Mix of amniotic fluid and gut debris in the foetus.

55
Q

What is bilirubin from in pregnancy?

A

Haemoglobin breakdown in foetus and mother.

56
Q

How is bilirubin excreted in pregnancy?

A

Mother excretes it via bile, conjugated.

Foetus has bilirubin cross placenta as it can’t conjugate it itself so mother excretes it.

57
Q

Why might a neonate become jaundiced?

A

If conjugation doesn’t establish quickly.

58
Q

How can neonatal jaundice be treated?

A

Phototherapy to stimulate the liver to begin conjugation.

59
Q

What is meant by the placenta being haemomonochorial?

A

Thin barrier.

60
Q

What is the driving force of movement across the placenta?

A

Gradient of partial pressures between maternal and umbilical blood.

61
Q

What is rate of oxygen transport determined by?

A

pO2 of umbilical artery.

62
Q

Why can labour be a problem to O2 of the foetus?

A

They only have small stores of oxygen and contraction of the myometrium can compress the placenta blood vessels.

63
Q

What is the double Bohr effect in pregnancy?

A

Increased pCO2 or [H+] mean haemoglobin lose affinity for oxygen so release it. This happens in the maternal and foetal blood.

64
Q

How is CO2 transferred in pregnancy?

A

Maternal pCO2 is lowered by hyperventilation stimulated by progesterone to make the concentration gradient favourable for foetus to get rid of CO2.

15. Reproductive (12 decks)

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