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SA reproductive > S7) Foetal Growth and Development > Flashcards

S7) Foetal Growth and Development Flashcards

1
Q

What is the foetal period and what happens during this?

A
  • The foetal period is the period involving preparation for the transition to independent life after birth
  • Growth and physiological maturation of the structures created during the embryonic period occurs
  • from 9 weeks gestation
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2
Q

What characterises the embryonic period?

A

Embryonic period is characterised by intense activity (organogenetic period) but absolute growth is very small

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3
Q

What is crown-rump length?

A

Crown-rump length (CRL) is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump)

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4
Q

Describe the differential growth observed in the crown-rump length

A

CRL increases rapidly in the pre-embryonic, embryonic & early fetal periods

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5
Q

Describe how weight gain varies in the different foetal periods

A
  • Embryo – intense morphogenesis & differentiation; little weight gain; placental growth most significant
  • Early foetus – protein deposition
  • Late foetus – adipose deposition

in the last stages the foetal growth increases rapidly

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6
Q

Explain how body proportions change during the foetal period

A
  • 9 weeks, the head is approx half crown-rump length
  • Thereafter, body length & lower limb growth accelerates
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7
Q

Identify and describe 3 different ways of assessing foetal well-being

A
  • Mother – foetal movements
  • Regular measurements of uterine expansion – symphysis-fundal height
  • Ultrasound scan
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8
Q

Obstetric ultrasound scan (USS) is routinely carried out at ~20 weeks.

Identify 5 advantages of this

A
  • Safe
  • Can be used early in pregnancy to calculate age
  • Rules out ectopic pregnancy
  • Indicates number of foetuses
  • Assess foetal growth and anomalies
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9
Q

Identify and describe 2 different ways of estimating foetal age

A
  • Last menstrual period (LMP) – prone to inaccuracy
  • Developmental criteria – allows accurate estimation of fetal age
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10
Q

Why and when do we measure crown-rump length?

A

Measured between 7 & 13 weeks to date the pregnancy and estimate EDD

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11
Q

What is biparietal diameter and when is it used?

A
  • Biparietal diameter is the distance between the parietal bones of the fetal skull
  • Used in combination with other measurements to date pregnancies in T2 & T3
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12
Q

When is abdominal circumference and femur length used?

A
  • AC & FL used in combination with BPD for dating and growth monitoring
  • Useful for anomaly detection
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13
Q

How do we classify birth weights?

A
  • Average: 3500 g
  • Growth restriction: < 2500 g
  • Macrosomia: > 4500 g (maternal diabetes)
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14
Q

Provide 3 possible reasons for low-birth weight

A
  • They are premature
  • They are constitutionally small
  • They have suffered growth restriction (associated with neonatal morbidity & mortality)
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15
Q

The lungs develop relatively late.

Why is this?

A
  • Embryonic development creates only the bronchopulmonary tree
  • Functional specialisation occurs in the foetal period
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16
Q

Identify the different stages in the development of the respiratory system

A
  • Weeks 8 – 16: pseudoglandular stage
  • Weeks 16 – 26: canalicular stage
  • Weeks 26 – term: terminal sac stage
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17
Q

Describe the pseudoglandular stage in lung development weeks 8-16

A
  • Duct system begins to form within the bronchopulmonary segments created during the embryonic period
  • Forms bronchioles
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18
Q

Describe the canulicular stage in lung development weeks 16-26

A

Formation of respiratory bronchioles through budding from bronchioles formed during the pseudoglandular stage

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19
Q

Describe the terminal sac stage in lung development week 24→

A
  • Terminal sacs begin to bud from the respiratory bronchioles
  • Type I & Type II pneumocytes differentiate
  • Surfactant is produced
20
Q

Gas exchange is conducted at placenta, but lungs must be prepared to assume full burden at birth.

How does this happen in T2 and T3?

A
  • “Breathing” movements condition of the respiratory musculature
  • Fluid filled spaces crucial for normal lung development
21
Q

Discuss the threshold for viability in terms of pre-term survival

A

Viability is only a possibility once the lungs have entered the terminal sac stage of development (> 24 weeks)

22
Q

Respiratory distress syndrome often affects infants born pre-maturely and involves insufficient surfactant production.

How can this be treated?

A

Glucocorticoid treatment (of the mother) increases surfactant production in foetus if preterm delivery is inevitable/unavoidable

23
Q

When is the definitive foetal heart rate determined?

A
  • The definitive fetal HR is achieved at around 15 weeks
  • Foetal bradycardia is associated with fetal demise
24
Q

Describe the development of the urinary system in the foetus and the importance of such

A
  • Foetal kidney function begins in week 10
  • Foetal urine is a major contributor to amniotic fluid volume
25
Q

Describe the variations in amniotic fluid volume

A
  • Oligohydramnios: too little amniotic fluid due to placental insufficiency or fetal renal impairment
  • Polyhydramnios: too much amniotic fluid due to foetal abnormality e.g. inability to swallow
26
Q

The nervous system is first to begin development and last to finish.

Briefly outline its development

A
  • Corticospinal tracts required for coordinated voluntary movements to begin to form in the 4th month
  • Myelination of brain only begins in 9th month
27
Q

Outline the development of sensory and motor systems

A
  • No movement until the 8th week
  • Thereafter a large repertoire of movements develop to “practise” for post-natal life e.g. suckling, breathing
28
Q

What is “quickening” and what is its the benefit?

A
  • Quickening is the maternal awareness of fetal movements from 17 weeks onwards
  • It is a low cost, simple method of ante-partum fetal surveillance and reveals those foetuses requiring follow-up
29
Q

In terms of chronology, compare and contrast the development of the brain and lungs

A
30
Q

Identify 3 benefits of transvaginal ultrasound

A
  • Check that conceptus implanted in correct place
  • Rule out ectopic pregnancy
  • Check for multiple foetuses
31
Q

Why are dietary supplements of folic acid recommended during pregnancy?

A

Folic acid prevents neural tube defects

32
Q

When can you hear a foetal heartbeat with a:

  • Doppler stethoscope
  • Plain stethoscope
A
  • Doppler stethoscope: 10-12 weeks
  • Plain stethoscope: after 20 weeks
33
Q

What is the average foetal heart rate at term?

A

110 - 160 bpm at term (37 weeks)

34
Q

Which cells secrete surfactant?

A

Type II pneumocytes

35
Q

At what gestational age does surfactant production begin and how is this significant in prematurity?

A
  • Surfactant begins production at 24-28 weeks
  • Majority of surfactant is produced by 35 weeks, hence is insufficient in premature babies
36
Q

What is symphysis-fundal height ?

A

Symphysis-fundal height is the distance from the pubic symphysis and the fundus of the uterus used to assess foetal growth and development during pregnancy

37
Q

Identify 3 sources of error for the symphysis-fundal assessment

A
  • Human error (poor technique)
  • More/less than normal amniotic fluid volume
  • Later in pregnancy (foetal engagement, head moves, smaller fundus)
38
Q

Which factors must be considered in deciding whether to allow a compromised foetus to remain in utero?

A
  • Mother’s health
  • Foetal viability
  • Stage of pregnancy
39
Q

How is amniotic fluid produced prior to week 8?

A

Amniotic fluid is produced by foetal cells in the amnion

40
Q

Identify 5 conditions which would lead to decreased amniotic fluid volume

A
  • Foetal kidney malfunction
  • Maternal hypertensive disorders
  • Premature rupture of membranes
  • Foetal bladder outlet obstruction
  • Premature leakage of amniotic fluid
41
Q

The foetus swallows and digests amniotic fluid.

Identify a foetal GI tract defect that might lead to polyhydramnios

A

Defect in the tracheal oesophageal septum leads to blind-ended oesophagus (atresia) or fistula

42
Q

Identify 5 instances when a foetus would be classified as at-risk

A
  • Growth restriction
  • Macrosomia
  • Poorly positioned
  • Multiple foetuses
  • Pre-eclamptic mother
43
Q

classification on birth rates

A

LOW: less than 2.5kg

very low: 1-1.5kg

extremely low: 1kg

macrosomia>4kg

44
Q

what is symmetrical intraauterine growth restriction

A
  • head, abdominal, biparietal circumference and diameter are all proportionally smaller
  • caused by genetic disorders, TORCH infections
  • occurs earlier on
45
Q

what is asymmetrical intrauterine growth disorders

A
  • abdominal circumference reduced
  • head, femur and biparietal diameter are all normal
  • due to placental insufficiency (pre-eclampsia)
  • occurs later on
46
Q

what happens in respiratory distress syndrome

A
  • affects infants born prematurely
  • insufficent surfactant production
47
Q

urinary system

A
  • fetal kidney development starts at week 10
  • fetal urine is a major contributor to amniotic fluid volume
  • kidney function not necessary in utero but without it there is olgiohtdeamnios

SA reproductive (22 decks)

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