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Reproduction, development and ageing > Foetal growth > Flashcards

Foetal growth Flashcards

1
Q

Define foetal growth.

A

Increase in mass that occurs between the end of the embryonic period and birth.

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2
Q

Give an example of measurement of foetal growth.

A

Crown-rump length (CRL).

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3
Q

What can result from an interruption in placental development?

A

Can cause foetal growth restriction (early on) or failure to achieve predetermined foetal weight at the end of pregnancy- reduced foetal weight gain (later on).

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4
Q

What are the 2 components that foetal growth depends on?

A

Genetic potential- derived from both parents, mediated through growth factors, e.g. insulin like growth factors.

Substrate supply- essential to achieve genetic potential, derived from placenta which is dependent upon both uterine and placental vascularity.

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5
Q

What 3 phases is normal foetal growth characterised by?

A

Cellular hyperplasia

Hyperplasia and hypertrophy

Hypertrophy alone

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6
Q

How is foetal size assessed?

A

Abdominal palpation

Symphysis fundal height (SFH)

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7
Q

What are the pros and cons of using symphysis fundal height (SFH) as a measurement of foetal size?

A

Simple

Inexpensive

Low detection rate: 50-86%

Great inter-operator variability

Influenced by a number of factors (BMI, foetal lie, amniotic fluid, fibroids)

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8
Q

What is symphysis fundal height?

A

Distance over the abdominal wall from the symphysis to the top of the uterus.

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9
Q

What are the expected symphysis fundal heights (SFH) at different gestational ages?

A

12w: at symphysis pubis
20w: at umbilicus
20-34w: GA ± 2cm
36-38w: GA ± 3cm
>38w: GA ± 4cm

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10
Q

What is the expected pattern of foetal weight gain over different gestational ages?

A

14-15wks: 5g/day
20wks: 10g/day
32-34wks: 30-35g/day
>34wks: growth rate decreases

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11
Q

What may be the reason for a smaller than expected symphysis fundal height (SFH)?

A

Wrong dates
Small for gestational age
Oligohydramnios
Transverse lie

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12
Q

What may be the reason for a larger than expected symphysis fundal height (SFH)?

A 
Wrong dates
Molar pregnancy
Multiple gestation
Large for gestational age
Polyhydramnios
Maternal obesity
Fibroids
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13
Q

What is the importance of correct dating of a pregnancy?

A

SGA or LGA confusion
Inappropriate inductions
Steroids in preterm delivery

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14
Q

How should pregnancies be dated?

A

All pregnancies should be dated by CRL except IVF pregnancies.

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15
Q

What is the problem with dating by last menstrual period (LMP)?

A

Inaccurate (irregular periods, abnormal bleeding, oral contraceptives, breastfeeding).

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16
Q

When is head circumference used to date a pregnancy?

A

If the first scan is done after 14 weeks (CRL >84mm).

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17
Q

How is foetal growth assessed through ultrasound?

A

Foetal growth is assessed by 4 biometrical parameters (biparietal diameter BPD, head circumference HC, abdominal circumference AC, femur length FL) and their combination (estimated foetal weight EFW).

Normative growth curves constructed from ultrasound measurements are expressed in centiles.

They are used clinically to identify a normal intrauterine growth and detect risk of obstetric and neonatal complications.

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18
Q

What maternal factors influence foetal growth?

A 
Poverty
Age
Drug use
Weight
Disease: hypertension, diabetes, coagulopathy
Smoking and nicotine
Alcohol
Diet
Prenatal depression
Environmental toxins
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19
Q

What foeto-placental factors influence foetal growth?

A

Genotype- genetic potential
Gender (M>F)
Hormones
Previous pregnancy

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20
Q

What is the purpose of obstetric ultrasound examination?

A

Assessment of foetal ‘wellness’, not just size.

Looking at trends in growth.

Predicting foetal metabolic compromise.

Anticipating the need to deliver prematurely.

Liaising with neonatal services.

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21
Q

What are the 3 underlying principles of the customised growth chart standard that define the individual foetal growth potential?

A

Adjusted to reflect maternal constitutional variation maternal height, weight, ethnicity, parity.

Optimised by presenting a standard free from pathological factors such as diabetes and smoking.

Based on foetal weight curves derived from normal pregnancies.

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22
Q

Define ‘small for gestational age’, SGA.

A

Birth weight < 10th centile.

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23
Q

Define ‘foetal growth restriction’, FGR.

A

Failure of the foetus to achieve its predetermined growth potential.

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24
Q

What is defined as very low birth weight?

A

<1500g

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25
Q

What is defined as low birth weight?

A

<2500g

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26
Q

What are the short-term problems associated with low birth weight/foetal growth restriction/prematurity?

A 
Respiratory distress
Intraventricular haemorrhage
Sepsis
Hypoglycaemia
Necrotising enterocolitis
Jaundice
Electrolyte imbalance
27
Q

What are the medium-term problems associated with low birth weight/foetal growth restriction/prematurity?

A

Respiratory problems
Developmental delay
Special needs schooling

28
Q

What are the long-term problems associated with low birth weight/foetal growth restriction/prematurity?

A

Foetal programming.

29
Q

What are the causes of SGA (small for gestational age)?

A

Dating problem:

  • consistent growth
  • normal dopplers and fluid

Normal:
-growth may reduce in 2 weeks
normal dopplers and fluid

Foetal problem 5%:

  • foetal abnormality
  • foetal infection

Placental insufficiency 20%:

  • reduction in AC/FL
  • reduced liquor
  • deranged dopplers
30
Q

What are the maternal medical factors associated with foetal growth restriction and SGA (small for gestational age) foetuses?

A 
Chronic hypertension
Connective tissue disease
Severe chronic infection
Diabetes mellitus
Anaemia
Uterine abnormalities
Maternal malignancy
Pre-eclampsia
Thrombophilic defects
31
Q

What are the maternal behavioural factors associated with foetal growth restriction and SGA (small for gestational age) foetuses?

A 
Smoking
Low booking weight (<50kg)
Poor nutrition
Age <16 or >35 years at delivery
Alcohol
Drugs
High altitude
Social deprivation
32
Q

What are the foetal factors associated with foetal growth restriction and SGA (small for gestational age) foetuses?

A 
Multiple pregnancy
Structural abnormality 
Chromosomal abnormalities
Intrauterine (congenital) infection
Inborn errors of metabolism
33
Q

What are the placental factors associated with foetal growth restriction and SGA (small for gestational age) foetuses?

A 
Impaired trophoblast invasion
Partial abruption or infarction
Chorioamnionitis
Placental cysts
Placenta praevia
34
Q

How long is the period of placentation?

A

10-12 weeks.

35
Q

What hormones from the pituitary may contribute to foetal growth?

A

Somatotrophin- (small?), partly via hepatic growth factors.

FSH/LH- via gonadal steroid production.

Not prolactin.

36
Q

What hormone from the pancreas may contribute to foetal growth?

A

Insulin.

37
Q

What hormones from the adrenals may contribute to foetal growth?

A

Androgens.

38
Q

What hormones from the gonads may contribute to foetal growth?

A

Androgens.

39
Q

What hormones from the thyroid may contribute to foetal growth?

A

Iodothyronines- probably by third trimester.

40
Q

What foetuses may the term ‘foetal growth restriction’ be used for, and why?

A

The term FGR should only be used for foetuses with definite evidence that growth has altered.

Growth is a dynamic process of a change of size over time and, therefore, it can only be assessed by serial observation.

41
Q

How is a centile chosen for use in assessing foetal growth rates?

A

A balance between sensitivity and specificity is made- the 10th centile is most sensitive and the 3rd centile is most specific.

The 10th centile will capture all babies with foetal growth restriction, but will also include babies that are just small for gestational age, i.e. you get a number of false positives.

All babies recorded using the 3rd centile will have foetal growth restriction, but some foetal growth restricted babies may be missed, i.e. you get a number of false negatives.

42
Q

What are the short- and long-term sequelae of foetal growth restriction (FGR)?

A

Intrauterine growth restriction (IUGR) is the most common factor identified in stillborn babies.

It has serious consequences for babies who survive.

There is an increased risk of IUGR and intrauterine death in mother’s subsequent pregnancy.

43
Q

What happens in the first phase of placentation (10-12 weeks)?

A

First trimester.

Rapid early growth prepares way for foetal growth.

Trophoblast cells use same molecular mechanisms as tumours, but are highly regulated and controlled.

44
Q

What factors determine nutrient demand, placental supply and foetal nutrition?

A 
Foetal genome
Maternal body composition
Utero-placental blood flow
Dietary intake
Placental transfer
45
Q

How does foetal nutrition influence foetal growth?

A

Oxygen and blood flow
Nutrient supply, glucose, amino acids, fatty acids
Endocrine regulation, IGFs, PGH, leptin

46
Q

What is preeclampsia?

A

Hypertension
Oedema
Proteinuria
Multisystem disease that usually manifests as hypertension and proteinuria.

47
Q

Which foetuses need growth monitoring?

A

Bad obstetric history:

  • previous maternal hypertension
  • previous FGR
  • stillbirth
  • placental abruption

Concerns in index pregnancy:

  • abnormal serum biochemistry
  • reduced symphysis fundal height
  • maternal systemic disease, e.g. hypertension, renal, coagulation
  • antepartum haemorrhage
48
Q

What ‘at risk’ pregnancies are screened at 24 weeks?

A

PAPP-A <0.4MoM (hormone used for screening for Down’s syndrome, automatically get serial growth scans at this low level), POHx PET/FGR.
Maternal systemic disease, e.g. HT, renal, sickle.
Uterine artery doppler 1st/2nd trimester- blood flow through uterine arteries- identify high resistance flow.

49
Q

What is the sequence of events in foetal growth restriction?

A

Uterine artery- high sheering force coming to the placenta (increased blood flow)- maternal circulation is abnormal.
Umbilical artery resistance increased- placenta fails.
Reduced foetal movements.
Foetus tries to compensate by diverting blood to vital organs such as brain and heart.
Decreased blood flow through middle cerebral artery to placenta.
Reduced amniotic fluid volume- kidneys shut down.
Blood flow through ductus venosus to placenta increased.
Intrauterine death.

50
Q

What percentage of preeclampsia patients will develop a severe form of preeclampsia?

A

1-2%

51
Q

What percentage of all pregnancies does the mother have high blood pressure?

A

10%

52
Q

What is foetal syndrome and how common is it?

A

Foetal growth restriction without preeclampsia.

Relatively rare.

53
Q

What is the role of doppler ultrasound in assessing a pregnancy?

A

Blood flow through umbilical arteries (placental blood flow) and uterine arteries.

54
Q

When does increased impedance in the umbilical arteries become evident?

A

When at least 60% of the placental vascular bed is obliterated- abnormal umbilical artery blood flow.

55
Q

What happens when the foetus becomes hypoxic?

A

CNS dysfunction leading to:

  • poor tone
  • altered breathing
  • altered movement patterns
  • changes in heart rate patterns

Aortic body chemoreceptor stimulation, leading to redistribution of cardiac output. This leads to increased flow to the brain, heart and adrenals, and decreased flow to the lungs, kidneys and gut.

56
Q

Describe the foetal circulation.

A

25% of blood flow from the umbilical vein passes through the ductus venosus, intrahepatic, AC growth.
Foetal lungs are inactive in utero- right ventricle is dominant, blood is shunted through the foramen ovale.
Foetal perfusion of renal system- amniotic fluid production.

57
Q

How are foetal movements counted?

A

A reduction in foetal movements may precede foetal death by a day or more, therefore, foetal movement counting may be of value in assessing foetal wellbeing.
In the UK, the Cardiff kick chart is the most commonly used method.
Mothers record the time taken each day to feel ten foetal movements.
Women who report a reduction in foetal movements, and particularly those who report an absence of foetal movements, need cardiotocography and/or an ultrasound assessment of the foetus to reassure the mother and ensure foetal wellbeing.

58
Q

What are the general principles of management of foetal growth restricted pregnancies?

A

Problems in the index pregnancy- manage according to serial foetal biometry, foetal doppler, BPP and CTG.
Screening of ‘at risk’ pregnancies- 24/40 Ut A screening.
Delivery- aim to deliver when >28 weeks and/or >500g, Caesarean section for compromised features.

59
Q

How is the timing of delivery of foetal growth restricted pregnancies determined, and neonatal wellbeing optimised?

A

Timing delivery in these pregnancies depends on balancing the risks to the foetus if it remains in utero and the hazards from the prematurity, which decrease as the gestation advances.
Identify evidence of foetal compromise on CTGs or abnormal dopplers/ ultrasound finding/ maternal compromise.
Corticosteroids should be administered (if not already given) at gestations <36 weeks in order to improve neonatal wellbeing.

60
Q

What does the mode of delivery in foetal growth restricted pregnancies depend upon?

A 
Gestation of the pregnancy
Condition of the pregnancy
State of the cervix
Presentation of the foetus
Other factors: oligohydramnios
Labour may be poorly tolerated due to cord compression
61
Q

What is the incidence of early intrauterine growth restriction?

A

Low- 1%.

62
Q

What is the incidence of late intrauterine growth restriction?

A

More common- 5-7%.

63
Q

Compare early and late intrauterine growth restriction.

A

Early IUGR:

  • low incidence 1%
  • highly correlated to maternal disease (preeclampsia)
  • difficult to manage- balancing risks of severe prematurity and morbidity with risk of in utero death

Late IUGR:

  • more common 5-7%
  • rarely correlated to preeclampsia
  • difficult to differentiate from constitutionally SGA
  • easy to manage: deliver

Reproduction, development and ageing (9 decks)

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