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Reproductive systems > Foetal growth and development > Flashcards

Foetal growth and development Flashcards

1
Q

What is the foetal period?

A
  • From 9 weeks gestation
  • Growth and physiological maturation of structures created during embryonic period
  • Involves preparation for transition to independent life after birth
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2
Q

Compare patterns of growth in the embryonic period versus the foetal period

A
  • Embryonic period is characterised by intense activity but absolute growth is very small (except placental)
  • Placental growth most significant in embryonic period
  • Growth and weight gain accelerate in foetal period
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3
Q

Outline stage one of normal intrauterine growth

A
  • Hyperplasia
  • 4-20 weeks
  • Rapid mitosis
  • Increasing DNA content
  • Symmetric
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4
Q

Outline stage 2 of normal intrauterine growth

A
  • Hyperplasia/hypertrophy
  • 20-28 weeks
  • Declining mitosis
  • Increasing cell size
    -Mixed - asymmetric
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5
Q

Outline stage 3 of normal intrauterine growth

A
  • Hypertrophy
  • 28-40 weeks
  • Rapid hypertrophy
  • Rapid increasing cell size
  • Rapid accumulation of fat, muscle, connective tissue
  • Asymmetric
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6
Q

Outline differential growth throughout the different periods of pregnancy

A
  • Crown rump length increases rapidly in pre-embryonic, embryonic and early foetal periods
  • Weight gain is slow at first, then increases rapidly in mid and late foetal periods
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7
Q

What is the difference between deposition in the early foetus and the late foetus?

A
  • Early foetus - protein deposition
  • Late foetus - adipose deposition
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8
Q

How do body proportions change during the foetal period?

A
  • At 9 weeks the head is approximately half crown-rump length
  • Thereafter, body length and lower limb growth accelerates
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9
Q

How is foetal wellbeing assessed before birth?

A
  • Foetal movements (start at 8 weeks and can be felt by mother at 20 weeks)
  • Regular measurements of uterine expansion
  • Ultrasound scans
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10
Q

How do we measure uterine expansion?

A
  • Symphysis-fundal height
  • Measured from top of uterus to pubic bone
  • Normally = number of weeks +/- 2cm
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11
Q

What are the different obstetric ultrasound scans?

A
  • 12 week scan
  • 20 week scan
  • Additional scans for growth measurement/ to assess foetal wellbeing
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12
Q

What is checked for at 12 week scans?

A
  • Determines gestational age
  • Detects multiple pregnancies
  • Screening for chromosomal abnormalities if opted for
  • Nuchal translucency scan
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13
Q

What is checked for at 20 week scans?

A
  • Screen for foetal abnormalities (heart, kidney, spine)
  • Determine placental location (e.g. placenta praevia)
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14
Q

How do we estimate foetal age?

A
  • Last menstrual period (prone to inaccuracy)
  • Developmental criteria allow accurate estimation of foetal age
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15
Q

How is crown-rump length measured?

A
  • Measured between 7&13 weeks to date pregnancy and estimate EDD
  • Scan in T1 also used to check location, number, viability
  • Very accurate
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16
Q

What is the biparietal diameter?

A
  • Distance between parietal bones of foetal skull
  • Used in combination with other measurements to date pregnancies in T2 and T3
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17
Q

What is abdominal circumference and femur length?

A
  • Used in combination with biparietal diameter
  • Dating, growth monitoring, anomaly detection
18
Q

What is the average normal birth weight?

A
  • 3.5 kg
19
Q

How is low birth weight classified?

A
  • Less than 2.5 kg
  • Very low birth weight is between 1.0-1.5kg
  • Extremely low birth weight is up to 1.0 kg
20
Q

How is macrosomia defined?

A
  • > 4kg
21
Q

Why can babies have low birth-weight?

A
  • Premature
  • Constitutionally small
  • Have suffered growth restriction - associated with neonatal morbidity and mortality
22
Q

Outline symmetrical intrauterine growth restriction

A
  • Head circumference, abdominal circumference, biparietal diameter and foetal length are all proportionally reduced
23
Q

What causes symmetrical intrauterine growth restriction?

A
  • Genetic disorders
  • TORCH infections
24
Q

Outline asymmetrical intrauterine growth restriction

A
  • Abdominal circumference decreased
  • Biparietal diameter, head circumference and femur length are all normal
  • Brain sparing
  • Result of placental insufficiency (e.g. in pre-eclampsia)
25
Q

Give an overview of the development of the respiratory system?

A
  • Lungs develop relatively late
  • Embryonic development creates bronchopulmonary tree only
  • Major implications for pre-term survival
26
Q

Outline how the respiratory system develops between weeks 8-16

A
  • Duct system begins to form within bronchopulmonary segments created during embryonic period
  • These become bronchioles
  • Around 8 weeks foetus starts moving fluid out of lungs
27
Q

Outline how the respiratory system develops between 16-26 weeks

A
  • Formation of respiratory bronchioles
  • Budding from bronchioles formed during pseudoglandular stage
28
Q

Outline how the respiratory system develops at 26 weeks

A
  • Terminal sacs begin to bud from respiratory bronchioles
  • Cuboidal cells start differentiating to type I and type II pneumocytes
  • Pneumocytes produce surfactant needed for gas exchange
  • Gas exchange possible towards end of this stage (from 24 weeks onwards)
  • Tissue thins to assist gas exchange
29
Q

What happens to the lungs during T2 and T3?

A
  • Gas exchange is conducted at placenta, but lungs must be prepared to assume full burden at birth
  • ‘Breathing’ movements
  • Conditioning of respiratory musculature
  • Fluid filled - crucial for normal lung development
30
Q

How can we prevent premature birth?

A
  • Mum can be given steroids to help baby produce surfactant
31
Q

When is foetal viability possible?

A
  • Once lungs have entered terminal sac stage of development
  • > 24 weeks
32
Q

What is respiratory distress syndrome?

A
  • Often occurs in infants born prematurely
  • Insufficient surfactant production
  • If pre-term delivery is unavoidable or inevitable
  • Mother is treated with glucocorticoids
  • This increases surfactant production in foetus
33
Q

Outline the development of the foetal cardiovascular system

A
  • Foetal cardiovascular system ensures that oxygenated blood collected by umbilical vein at placenta is circulated around foetus
  • Definitive foetal H/R is achieved at around 15 weeks
  • Foetal bradycardia associated with foetal demise
34
Q

Outline the development of the foetal urinary system

A
  • Kidney function begins in week 10
  • Foetal urine is a major contributor to amniotic volume from 20 weeks onwards
  • Foetal kidney function is not necessary for survival in utero
  • Without it there is oligohydramnios
35
Q

What is oligohydramnios?

A
  • Too little amniotic fluid
  • Placental insufficiency
  • Foetal renal impairment
  • Premature rupture of membranes
  • Pre-eclampsia
36
Q

What is polyhydramnios?

A
  • Too much amniotic fluid
  • Foetal abnormality (e.g. oesophageal atresia/anencephaly)
  • Gestational diabetes
  • Foetal anaemia
  • Multiple pregnancy
37
Q

Outline the development of the foetal nervous system

A
  • First system to begin development and last to finish
  • Corticospinal tracts required for coordinated voluntary movements begin to form in 4th month
  • Myelination of brain only begins in 9th month
  • Corticospinal tract myelination is incomplete at birth - this is why infant mobility increases during 1st year of life
38
Q

Outline the development of foetal sensory and motor systems

A
  • No movement until 8th week
  • Thereafter a large repertoire of movements develop
  • Allows foetus to practise for post-natal life
  • E.g. suckling, breathing
  • Maternal awareness of foetal movements from 15-17 weeks onwards
39
Q

Give a timeline of foetal lung development

A
  • 9 weeks - lungs begin functional adaptation
  • 24 weeks - terminal air sacs appear, some surfactant production
  • 36 weeks - greatly increased surfactant production
40
Q

Give a timeline of foetal brain development

A
  • 16 weeks - cerebellar development, corticospinal tracts begin to form
  • 20 weeks - myelination begins in spinal cord
  • 28 weeks - characteristic gyri and sulci appear as cerebellar hemispheres grow larger than skull
  • 36 weeks - myelination begins in brain

Reproductive systems (20 decks)

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