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Loss and Renewal > Foetal development and growth > Flashcards

Foetal development and growth Flashcards

1
Q

What happens in week 1 (clinical gestation week 3)?

A

Sperm and ovum join = fertilisation

Forms into a morula then a blastocyst which then implants into the endometrial wall

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2
Q

What happens in week 2 (clinical gestation week 4)?

A

Bilaminar germ discs form = epiblast/hypoblast

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3
Q

What happens in week 3 (clinical gestation week 5)?

A

Trilaminar germ disc forms

  • Gastrulation
  • Ectoderm/Mesoderm/Endoderm - from these 3 layers all the rest of the body can form
  • Neurulation - by end of 4th week
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4
Q

When does folding of the embryonic disc occur and what ways does it fold?

A

Flat trilaminar disc to cylindrical embryo

  • cephalo-caudal folding
  • lateral folding
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5
Q

What happens in the embryonic period?

A

Organogenesis
Establishment of main organ systems
Post-fertilisation week 3-8 (clinical gestation 5-10 weeks)

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6
Q

What happens in the foetal period?

A

Maturation and growth of tissues and organs

Post-fertilisation weeks 9-38 (clinical gestation 11-40 weeks)

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7
Q

What are the different types of birth defects?

A 
Developmental disorders present at birth 
Types:
- structural = congenital anomaly
- functional = organ dysfunction 
- metabolic = enzyme/cellular defect
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8
Q

What are the causes of birth defects?

A

Genetic
Environmental
Multi-factorial inheritance
- interaction between genetic constitution and environmental factors

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9
Q

What are some different causes of congenital anomalies?

A

Malformation

  • incomplete or abnormal formation of structure
  • complete of partial absence of a structure
  • alteration of its normal configuration

Disruption

  • morphological alterations of already formed structure
  • destructive process e.g. amniotic bands

Deformation
- mechanical factors e.g. positional talipes

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10
Q

What are some different causes of chromosomal/genetic issues?

A

Multi-organ involvement - usually lethal /significant defect
Syndromes
- group of anomalies with a specific known cause eg. Down’s Syndrome
Association
- abnormalities which tend to occur together but the cause is not determined e.g. CHARGE
Sequence
- when a defect leads to a cascade of further abnormalities e.g. potters sequence - baby doesn’t have any kidneys and this subsequently means no urine is produced, leading to no amniotic fluid and this leads to multiple abnormalities

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11
Q

What are the clinical features of Down’s syndrome?

A
  • craniofacial appearance = flat nasal bridge, upslanted palpebral fissures, epicanthic folds, brushfield spots
  • single palmar crease and wide sandal gap
  • Hypotonia
  • Congenital heart defects - 40%
  • Duodenal atresia
  • variable learning difficulties
  • Alzheimer’s / Malignancy
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12
Q

What are the different genetic causes of trisomy 21?

A

Non-disjunction - 94-95%
Robertsonian translocation
Mosaicism

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13
Q

What are the determining factors of a teratogenic birth defects?

A

Timing
Dosage
Genetic constitution of the embryo

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14
Q

What are some different types of teratogens?

A

Drugs - alcohol, cocaine, thalidomide, anticonvulsants, antipsychotics
Environmental factors - organic mercury, lead
Infectious agents - rubella, CMV
Radiation - high levels of ionising radiation
Maternal factors - SLE, poorly controlled pre-existing DM
Mechanical factors - malformed uterus, oligohydramnios, amniotic band

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15
Q

Based upon the timing of the foetus’ life, what impact does insult to teratogens have on the foetus?

A

Prior to post-fertilisation week 2
- either a miscarriage or no effect
Organogenesis period (weeks 3-8)
- period of greatest sensitivity to malformation
- different organ systems have different periods of peak sensitivity
- leading to birth defect
Foetogenesis period (weeks 9-38)
- main effect on growth and functional maturation
- usually not leading to birth defect

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16
Q

What is omphalocele?

A

Abdominal wall defect
- transparent sac of amnion attached to umbilical ring containing herniated viscera
1 in 4,000 births
Persistence of embryonic midgut herniation
60% associated with other abnormalities
20% chromosomal abnormalities e.g. Edwards

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17
Q

What is gastroschisis?

A

Abdominal wall defect

  • Evisceration of foetal intestine through a paraumbilical wall defect - to the R of the umbilicus
  • 1 in 4,000 births but increasing
  • Possible origins: involution of right umbilical vein or right viteline artery, abnormal body wall folding
  • associated with young mums, smoking and drug use
  • good prognosis after surgical correction
18
Q

How can you detect for congenital anomalies ?

A

Genetic testing

  • screening e.g. down’s syndrome
  • pre-implantation genetic diagnosis
  • invasive testing and non-invasive testing: single gene disorders, chromosomal abnormalities

Imaging
- Detailed foetal anomaly scan for structural anomalies - week 20

19
Q

What are the 2 examples of non-invasive prenatal testing (NIPT) for Down’s syndrome and how effective are they?

A

Shotgun = 98.6-100% detection rate

  • false positives= 0.2-2.1%
  • No results rate = 0.8 -3.9%

Targeted = 99.5-100% detection rate

  • false positives = 0-0.3%
  • no results rate = 0.8-4.6%
20
Q

What is foetoscopy?

A

foetoscopic laser ablation for foeto-foetal transfusion syndrome

21
Q

What is foetal blood sampling used for?

A

Foetal haemoglobin for anaemia
Foetal infection serology
Foetal blood transfusion

22
Q

What is encompassed in chorionic villus sampling?

A

Chromosome/microarray and DNA analysis

Enzyme analysis of inborn error of metabolism

23
Q

What is pre-implantation genetic diagnosis ?

A

In-vitro fertilisation allows genetic analysis of cells from a developing embryo before transfer to the uterus

24
Q

What is non-invasive genetic diagnosis?

A

Free foetal DNA obtained from maternal blood for identification of foetal gender and rhesus status

25
Q

What is amniocentesis?

A

Chromosome/Microarray analysis and DNA analysis

Foetal infection - PCR for CMV, Taxoplasmosis, rubella and parvovirus

26
Q

What are some other more risky foetal therapies?

A

Foetal surgery for spina bifida
- reduces need for shunting and motor function but significant risk to foetus and mother

Tracheal occlusion in congenital diaphragmatic hernia

27
Q

What is cleft lip and palate?

A

End of 4th week face is formed from 5 prominences, nasal pit forms and the maxillary prominence gets larger and expands moving towards the midline, natural fusions points between the maxillary prominence and medial nasal prominence
If these prominences don’t form properly it can lead to cleft lip
-Difficult to see cleft palate ante-natally much easier to see cleft lips

  • Very good cosmetic results after surgery
  • can be more complex and associated with other abnormalities or it can have no other associated problems
28
Q

What are some methods of preventing birth defects?

A

Vaccination e.g. rubella
Avoidance of teratogenic drugs/substances
Folic acid to decrease neural tube defects
Nutrition e.g. iodine
Optimise disease control e.g. diabetes
Maternal age

Pre-natal genetic diagnosis

29
Q

Define: IUGR

A

intrauterine growth restriction

- failure of foetus to achieve his or her growth potential

30
Q

Define: SGA

A

Small for gestational age

- infant is below a particular weight centile for gestation - normally the 10th centile is chosen

31
Q

Why is growth restriction important?

A 
3-10% of births 
Can cause intrauterine death 
Causes increased perinatal morbidity and mortality 
- birth asphyxia
- hypoglycaemia
- hypothermia
- mortality
32
Q

What is growth in utero dependent on?

A

Maternal factors
Foetal factors
Placental factors

33
Q

What maternal factors are involved in intrauterine foetal development?

A 
Ethnicity
Maternal stature/BMI
- maternal vs paternal influence
Drugs 
- cigarettes, alcohol, drugs of abuse
Nutrition 
Maternal hypoxia 
- cyanotic heart disease, chronic respiratory disease, altitude
34
Q

What foetal factors are involved in intrauterine foetal development?

A

Genome - chromosomal disorders
Growth factors - insulin like growth factors, thyroxine
Congenital infection - CMV, toxoplasmosis, rubella

35
Q

What placental factors are involved in intrauterine foetal development?

A

Primary placental problems - abnormality of placenta structure/function
Secondary placental problems - hypertension, chronic renal disease, vasculitis, pro-thrombotic disorders
Multiple gestation - growth discordance

36
Q

What happens in malplacentation in IUGR?

A

Incomplete conversion of maternal spiral arteries
- dilatation by loss of media, replaced by fibrinoid
Trophoblast invasion
- Interstitial trophoblast
- Endovascular trophoblast

37
Q

What is uteroplacental insufficiency?

A

decreased glycogen stores so decreased abdominal circumference
Asymmetrical patterns fo IUGR

38
Q

What is symmetrical patterns of IUGR?

A

Early growth insult, chromosomal, viral infection - disrupted regulation of growth processes or disruption at cell hyperplasia stage

39
Q

What is the Barker hypothesis?

A

Foetal programming

  • most show catch up growth in childhood although they may have a smaller size in adulthood
  • IUGR can have a lifelong impact though
40
Q

What impact can impaired maternal malnutrition have for the child in the future?

A 
Good evidence that increased risk of:
- obesity 
- type 2 diabetes
- BP, stroke, heart disease 
Secondary to changes in growth, metabolism and vasculature

Loss and Renewal (6 decks)

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