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what are the 5 types of congenital abnormalities?
- 1. structural defect: diaphragmatic hernia
- 2. chromasomal abnormalities: trisomy 21 Downs
- 3. inherited abnormalities: cystic fibrosis
- 4. intrauterine infection: rubella
- 5. drug exposure: AEDs
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what is the aim of a screening test?
to identify subjects at INCREASED RISK for a given condition
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what is sensitivity?
% of people with the condition that are detected by the test
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what is specificity?
the % of people that DO NOT have the condition and test negative
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what is PPV?
% of people who test positive and have the disease
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what is NPV?
% of people who test negative and don't have the disease
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what level in the blood is raised in neural tube defects that can be detected on maternal blood testing?
AFP - product of fettle liver
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how are NTD confirmed and at what age?
16 weeks ultrasound
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give 3 differential for raised AFP in pregnancy
- 1. NTD
- 2. gastroschisis: free loops of bowel in amniotic cavity
- 3. high risk of third trimester complications
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when is amniocentesis safest performed?
16 weeks
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which diseases can be diagnosed on amnio? think of 3 categories
- 1. chromosomal abnormalities
- 2. infections: toxoplasmosis and CMV
- 3. inherited disorders: sickle cell, thalassaemia, cystic fibrosis
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what % of women miscarry after amniocentesis?
1%
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when can CVS be done?
11 weeks+
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what is CVS?
biopsy of trophoblast
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what are the advantages of CVS over amnio?
- 1. get result quicker
- 2. as test is done earlier in gestation, it allows abnormal fetes to be identified at a time when abortion can be done under GA if wanted
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what is the miscarriage rate of CVS compared to amnio and why?
- CVS higher than amnio
- because it is performed earlier when spont misc is more common
- and because more difficult procedure
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what is PGD and in which setting can it be used?
- pre-implantation genetic diagnosis
- IVF: cells from an embryo removed for genetic analysis before embryo is transferred to uterus to allow selection and only implant those that not affected by disorder which is tested
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how many live births are affected by chromosomal abnormalities?
6/1000
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what is the most common chromosomal abnormality among live births?
trisomy 21
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what is Downs usually the result of?
- random
- non-dysjunction (failure of chromosome pairs to separate properly during cell division)
- at meiosis
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what can Downs sometimes be caused by?
balanced chromosomal translocation in the parents
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what are the features of Down's syndrome?
- flat occiput
- single palmar crease
- high arch palate
- heart: AVSD
- learning difficulties
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what are the soft markers of Downs on USS?
- echogenic bowel,
- echogenic intracardiac focus, and
- dilitation of the kidneys
- smaller nose
- cant see stomach - tracheoesophageal fistula
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what % of downs have cardiac problems?
50%
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what is the risk of recurrence of having another child with downs? and what does it depend on?
- recurrence risk is low
- determined largely by maternal age
- unless there is a balanced translocation
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name 4 ultrasound features with give high risk for downs
- 1. nuchal translucency
- 2. structural abnormalities
- 3. tricuspid regurgitation
- 4. absent or short nasal bone
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what are the 2 different types of tests you can have in the 1st trimester as screening for downs?
- 1. nuchal translucency alone
- 2. combined test
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what is the combined test for down's syndrome? and when can they be done?
- nuchal translucency
- serum beta HCG
- serum PAPPA
- between 11-14 weeks
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what are the 3 different types of tests you can have in the 2nd trimester as screening for downs?
- double test: measure uE3 and beta HCG
- triple test: uE3, beta HCG, AFP
- quadruple test: eE3, beta HCG, AFP and inhibinA
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what does uE3 stand for and what is it made by? and what are the levels in Downs?
- unconjugated estriol
- made by placenta and fettle adrenals
- levels REDUCED in downs
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what is PAPPA made by and what happens to levels in downs?
- pregnancy associated plasma protein A
- made by placental syncytiotrophoblasts
- levels REDUCED in downs
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what is beta HCG made by and what happens to levels in downs?
- placenta
- INCREASED in downs
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what makes AFP and what happens to levels in downs
- fettle yolk sac and liver makes it
- REDUCED level in downs
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what makes inhibin-A and what happens to levels in downs?
- placenta
- INCREASED levels in downs
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what are the 2 different types of tests you can have in the 1st trimester as screening for downs?
what
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what is klinefelter's syndrome?
47 XXY
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name 3 symptoms of klinefelters
- normal intellect
- small testes
- infertile
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