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Fetus Module > disorders of fetal growth > Flashcards

disorders of fetal growth Flashcards

1
Q

what is the definition of small for gestational age?

A

fetus less than 10th centile for age

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2
Q

what is the definition of large for gestational age?

A

greater than the 97th centile

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3
Q

what is the definition of IUGR?

A

fetus unable to achieve genetically predetermined size

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4
Q

what is the definition of low birth weight?

A

birth weight less than 2500grams (can be SGA or premature)

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5
Q

what are the 3 classifications of SGA?

A

normal small fetus (no abnormalities, normal umbilical artery doppler and liquor, no risk, no special care needed)
abnormal small fetus (chromosomal or structural abnormalities)
growth restricted fetus (placental dysfunction - appropriate treatment or delivery may improve prospects)

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6
Q

what percentage of SGA/FGR are just healthy small foetuses?

A

40% are normal small fetus
40% are growth restricted
20% are intrinsically small - chromosomal abnormality etc

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7
Q

what are the two classifications of fetal growth restriction?

A

symmetrical

asymmetrical

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8
Q

when does the insult occur in symmetrical FGR?

A

early in development so it affects growth processes and cell hyperplasia

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9
Q

when does the insult occur in asymmetrical FGR?

A

later in development - fetal brain disproportionately large compared to liver (>6) when normal is >3 brain:liver

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10
Q

what are the etiological factors for IUGR?

A 
maternal
fetal 
placental 
OR 
intrinsic 
extrinsic
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11
Q

what are the intrinsic factors of IUGR?

A

chromosomal aberrations
congenital structural defects
constitutional (genetic heritage)

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12
Q

what are the extrinsic factors of IUGR?

A 
maternal-placental-fetal infections 
uteroplacental perfusion 
chronic maternal disease 
substrate availability 
toxins
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13
Q

what are some maternal causes of FGR?

A

chronic disease (HTN, collagen vascular disease, renal disease, thyrotoxicosis, advanced DM, hemoglobinopathies)
pre-eclampsia
malnutrition
infection (toxoplasmosis, malaria, rubella, CMV, herpes, syphilis, listeriosis)
maternal drugs/medications (heroin, methadone, cocaine, cigarette smoke, alcohol, cytotoxic drugs, lithium, etc)

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14
Q

what are some fetal risk factors for IUGR?

A

multiple pregnancy
infections (TORCH, TB, malaria, parvo virus B19)
congenital malformations
extra-uterine pregnancy
placenta or umbilical cord defects
chromosomal abnormalities (trisomy 13,18,21)

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15
Q

what are some placental factors for IUGR?

A

uteroplacental insufficiency (defective trophoblastic invasion/placentation, maternal insertion of cord, reduced blood flow - pre-eclampsia, TTTS, decreased functioning mass - small placenta, abruption, praaevia post-term placenta)

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16
Q

what are the underlying mechanisms of IUGR?

A 
insufficient gas exchange and nutrient delivery to fetus 
maternal disease => decreased oxygen carrying capacity (cyanotic heart disease, smoking, haemoglobinopathy) 
dysfunctional oxygen delivery system (diabetes with vascular disease, HTN, autoimmune conditions)
placental damage ( smoking, thrombophilia, autoimmune disease)
17
Q

when is growth most vulnerable to maternal dietary deficiencies?

A

during peri-implantation and period of rapid placental development

18
Q

what is the role of arginine and plyamines in fetal development?

A

deficiency causes decreases in NOS which causes decreases in embryogenesis, placental angiogenesis and growth, therefore placental-fetal blood flow is decreases and so there is a decreases in nutrient and oxygen supply from mother to fetus resulting in decreased fetal growth and development

19
Q

what are epigenetic alterations and how do they occur in the fetus?

A 
stable alterations of gene expression through covalent modifications of DNA and core histones, by 2 mechanisms = DNA methylation and histone modification. 
nutritional status (insult/deficiency) can alter the fetal genome and imprint gene expression leaving a permanent "memory" throughout life
20
Q

what are the 3 main functions of the placenta?

A

metabolism
transport
endocrine

21
Q

what does the placenta transport?

A

gases = oxygen and carbon dioxide to and from baby
nutrients = glucose, AA, antibodies, bilirubin
drugs
infectious agents = CMV, rubella measles etc

22
Q

what types of transport are there in the placenta?

A

intact transport
partially consumed
metabolised
not transported

23
Q

what are the perinatal implications of IUGR?

A 
increased fetal morbidity and mortality 
iatrogenic prematurity 
fetal compromise in labour 
increased need for induction of labour and c- section 
10 x increase in late fetal deaths 
still birth 
prematurity (nec, throbocytopenia, temp instability, renal failure, hypos) 
asphyxia 
congenital malformations
24
Q

what are the long term consequences of IUGR?

A

abnormalities with HPG axis and cardiovascular disease
insulin resistance
metabolic syndrome

25
Q

what is the thrifty hypothesis?

A

metabolically deprived developing fetus becomes metabolically programmed for insulin resistance and impaired glucose metabolism
strong associations between FGR and elevated fasting glucose/insulin levels and T2DM

26
Q

how is IUGR managed?

A

reduce risk factors

27
Q

how is IUGR diagnosed?

A

difficult!
presence of risk factors,
clinically = serial maternal weight, symphysis-fundal height assessment (poor predictor) customised fundal height charts are better take into account maternal height, weight, parity and ethnicity
US = inadequate fetal growth, reduced amniotic fluid index, placental calcification

28
Q

what is measured on fetal US/biometry?

A 
Biparietal diameter 
head circumference 
Transverse cerebellar diameter 
femur length 
abdominal circumference 
ratios 
estimated fetal weight (EFW)
29
Q

what surveillance is there for fetal growth?

A 
serial scans 
non-stress test 
amniotic fluid assessment 
umbilical doppler 
biophysical profile assessment
30
Q

what are some ancillary invasive tests?

A

fetal karyotyping
fetal blood sampling
amniocentesis for LS ratio

31
Q

how can IGRU be prevented?

A

largely unpreventable
some evidence for: LDA, mini heparin, reduce maternal smoking, antibiotics to prevent/treat UTIs, antimalarial prophylaxis

32
Q

how is IUGR managed?

A

fetal surveillance until the risk of demise in utero demise exceeds the risk of delivery and prematurity

33
Q

define large for gestational age?

A

fetus above the 90th centile for gestation

34
Q

define macrosomia?

A

birth weight >4000grams regardless of gestational age

35
Q

what is the prevalence of macrosomia?

A

9-10% >4kg

36
Q

what are the risk factors for macrosomia?

A

maternal hyperglycaemia during pregnancy
previous macrocosmic infant
pre-pregnancy obesity/excessive maternal weight
male fetus
post-term gestation
parental height and race
maternal age <20 years

37
Q

how is birthweight estimated?

A

symphysis pubis - fundal height

ultrasound

38
Q

what are the problems f fetal overgrowth?

A

maternal diabetes
fetal demise
birth trauma - shoulder dystocia
neonatal hypoglycaemia

Fetus Module (18 decks)

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