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Human Reproduction > Fetal growth > Flashcards

Fetal growth Flashcards

1
Q

How can pregnancies be dated clinically?

A
  1. Date of last menstruation (about 14 days before fertilisation)
  2. Bi-parietal diameter measurement using ultrasound (~8-12 weeks)
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2
Q

What are the simple tests (no equipment required) for measuring fetal growth?

A
  1. Maternal weight gain
  2. Uterine fundal height
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3
Q

What are the measurments that can be taken with ultrasound to measure fetal growth?

A
  1. Biparietal diameter
  2. Head circumference
  3. Crown (top of head)/rump (buttocks) length
  4. Femur length
  5. Abdominal diameter
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4
Q

What are the definitions for abnormal fetal growth with regards to centile charts?

A
  1. Small for gestational age (SGA): Below 10th centile (indicates IUGR)
  2. Large for gestational age (LGA): Above 90th centile (indicates possibility for birth obstruction)
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5
Q

What are the types of IUGR?

A
  1. Symmetrical
  2. Asymmetrical
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6
Q

What is symmetrical IUGR?

A

The parts of the fetal body are all in proportion with each other, but the overall size is smaller than for gestational age. This usually indicates growth restriction beginning in the first trimester.

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7
Q

What are the causes of symmetrical IUGR?

A
  1. Intrauterine infections (e.g. toxoplasmosis)
  2. Aneuploidy (and other chromosomal defects)
  3. Maternal abuse of alcohol (fetal alcohol syndrome)
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8
Q

What is asymmetrical IUGR?

A

The head of the fetus is much larger than its body. This usually indicates growth restriction sometime in the third trimester, resulting in diversion of nutrients away from the periphery in order to sustain growth of CNS.

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9
Q

What are the causes of asymmetrical IUGR?

A
  1. Pre-eclampsia
  2. Malnutrition
  3. Placental insufficiencies
  4. Anaemia
  5. Hypertension
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10
Q

Which type of IUGR is most common?

A

Asymmetrical (3/4 of cases)

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11
Q

What are the maternal factors that affect fetal growth?

A
  1. Uterine size
  2. Altitude
  3. Nutrition
  4. Parity
  5. Socio-economic status
  6. Disease
  7. Stress
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12
Q

How does uterine size affect growth?

A

The smaller the uterine size, the smaller the fetus tends to be as a consequence of spatial restriction.

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13
Q

How does maternal nutrition affect growth?

A

Maternal malnutrition has different effects on fetal growth depending on stage of pregnancy (as was evident from Dutch hunger winter).

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14
Q

What effects on fetal growth did the Dutch hunger winter have for women at different stages of pregnancy?

A
  • If malnutrition in mother occurs in first trimester, but is restored thereafter, there is no decline in birth weight, but adult morbidity is increased.
  • If malnutrition in mother occurs in third trimester, but is restored thereafter, there is decline in birth weight, but risk of adult morbidity is unaffected.
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15
Q

How does altitude affect fetal growth?

A
  • Maternal O2 exposure (and thus O2 available to fetus) is severely reduced at higher altitudes, which reduces birth weight.
  • Average birth weight falls ~100g per 1000m above sea level.
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16
Q

How does parity affect fetal growth?

A

First baby tends to smaller than second baby because the uterus and maternal physiology becomes more adapted to pregnancy after first pregnancy, so subsequent pregnancies are more ‘efficient’.

17
Q

How does maternal socio-economic status affect fetal growth?

A
  • Low socio-economic status is correlated with low birth weight.
  • Several possible explanations for this phenomenon:
    1. Early (teenage) pregnancy: Small uterine size
    2. Malnutrition
    3. Smoking/drug abuse
18
Q

How does maternal disease affect fetal growth?

A

Maternal diseases such as hypertension and cardiac insufficiency can affect her ability to supply fetus with adequate nutrition, thus cause fetal growth restriction.

19
Q

How does maternal stress affect fetal growth?

A

Increased levels of cortisol in maternal circulation may cause premature birth.

20
Q

What are the placental factors that affect fetal growth?

A
  1. Blood flow
  2. Infarction
  3. Transporter expression
  4. Barrier function
21
Q

How does placental blood flow affect fetal growth?

A
  1. Failure for spiral arteries to remodel properly during placentation causes increased resistance in placental circulation.
  2. This reduces blood supply to fetus and predisposes to condition such as IUGR in fetus but also pre-eclampsia in mother.
22
Q

How does placental infarction affect fetal growth?

A

Ischaemia of the placenta and subsequent tissue damage can reduce the surface area of feto-maternal exchange interface and thus cause growth restriction.

23
Q

How does placental transporter expression affect fetal growth?

A

In response to placental stress (e.g. reduced oxygenation), there may be reduced expression of many of the specialist transporters required for adequate nutrient exchange between mother and fetus (e.g. for glucose and amino acids), thus causing fetal growth restriction.

24
Q

How does placental barrier function affect fetal growth?

A

Disruption of barrier may result in maternal hormones and other factors (e.g. cortisol) leaking into fetal circulation and causing abnormal growth.

25
Q

What are the fetal factors that affect fetal growth?

A
  1. Sex
  2. Genome
  3. Infection
  4. Endocrine
26
Q

How does fetal sex affect fetal growth?

A

As a general trend, males on average have greater dimensions compared to females, including:

  1. Birth weight
  2. Length
  3. Head circumference
27
Q

How does fetal genome affect fetal growth?

A

Fetal genetic abnormalities (e.g. aneuploidies) account for substantial proportion of IUGRs.

28
Q

How does fetal infection affect fetal growth?

A

Infections (e.g. rubella, HCMV, toxoplasmosis) also cause symmetrical IUGR.

29
Q

How does fetal endocrine factors affect fetal growth?

A
  • The most important endocrine regulators of fetal growth are probably IGFs.
  • Defects in IGF expression lead to growth abnormalities.
30
Q

What are the symptoms of Beckwith-Wiedemann syndrome?

A
  1. Macroglossia (large tongue)
  2. Macrosomia (large birth size)
  3. Organomegaly (enlargement of organs)
  4. Anterior abdominal wall defects
  5. Predisposition to childhood tumours
31
Q

What are the causes of BWS?

A

Over-expression of IGFII gene on chromosome 11 as result of epigenetic factors, including:

  1. Paternal uniparental disomy
  2. Abnormal imprinting resulting in activation of maternally imprinted IGF-II (normally deactivated).

Human Reproduction (21 decks)

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