Prenatal Flashcards
% major Fetal abns related to Chr abnormalities
20-25%
% improvement the detection rate of Chr abns using aCGH over largo typing
4-6%
Study comparing 5 array platforms
Huang and Crolla. 2010. Comp 5 array platforms and software- 12 samples- all needed comparable Dan concn. and DR=93-100%
Key aim with use of aCGH in prenatal setting
Need balance of optimal resolution and coverage. Targeted/low res array will miss abns and higher density will increase cnvous
Advantage of using aCGH in prenatal so
No culture req- increase tat, decrease cultural artefact, better DR, pick up cryptics
Disadvantage of prenatal aCGH
Poor quality and quantity of dna , miss balanced rea, miss lower level mosaic, triploidy missed,still need culture for f/u fish, cnvous->anxiety, counselling issues ass with cnvous and inc penetrance
How many extra cyto cryptic abnormalities are seen on aCGH
1-3% in some studies
What are prenatal aCGH best practice guidelines
None specifically, guidelines based on results of EACh study
Hillman et al 2011 reviewed outcomes of pCNV in prenatal setting- what are they?
12% cnv seen in all foetuses (3.6% were pathogenic), 11.2% cnv seen in abscan referrals (5.2% pathogenic)
When should a deletion of an autosomal recessive condition be reported
Only if carrier freq is high. Consider late onset with clinical utility
Definition of screening
Process to ID apparently healthy people at an increased risk of a condition. Can then be offered further tests or treatment to decrease risk and/or complications
3 considerations of effective screening
High DR, low FPR, low FNR
By 2010 all nhs trusts were expected to provide what DR and FPR for aneuploidy screen
> 90% dr and
What is the FASP
Fetal anomaly screening prog.overseen by uknsc.
Risk of trisomy 21 at 49 years
1:85
Risk if T21 at 30
1:940
Risk if T21 at 20
1:1450
Risk if T21 at 35
1:350
What was the DR for a 5% FPR when using maternal age only
DR 30%
What is the current DS screening uptake (according to RAPID)
66%
What is national target for timescale of offering one for high risk screen patients
97% in 3 days
what is MoM
Multiple of mean
How is MoM calculated
Concentration of marker for a patient divided by concentration of that marker in general popn
What is measured in triple test
Afp, beta hcg and uE3
Dr for 5% FPR for triple test
77%
What markers are measured in quad test
UE3, beta hcg, inhibinA and afp
Quad test dr for 5% FPR
81%
What is measured in combined test
NT, Papp-a and beta hcg
What is dr for 5% FPR for combined test
87%
What is integrated test
Trimester 1: nt, Papp-a and beta hcg. Trimester 2: afp ue3 and inhibin a
What is dr for 5% FPR for integrated test
96%
Why isn’t integrated test recommended
25% do not attend second appt
Factors affecting serum levels
Weight less in heavier women, Afro caribeans increased compared with Caucasian, Ivf pregnancies, smokers have lower Pappa hcg and higher inhibin-a, increased levels in twins
Future if prenatal trisomy screening
Nipt, proteomics using mat serum
Describe the marker AFP
Produced by yolk sac and liver, concn increases with gestation, increased in NTD and decreased inT21.
What marker results will be seen in T21 pregnancy
Decreased AFP, ue3 and increased Papp-a, beta hcg and inhibin a
What is papp-a marker
Pregnanc associated plasma protein a. Origin is placental synctiotrophoblast, increased in T21, pre eclampsia iugr, increase with gestation
What is ue3
Unconjugated estriol. Only produced in dig amounts by placenta. Increase concn with gestation. Decreased in T21
What is inhibin-a
Produced by placenta, decrease with gestation to 17wk then increase. Increased in T21
What is beta hcg
Peptide hormone, made by embryo soon after conception then by synctiotrophoblast. Concn decrease with gestation, screen sensitivity maintained in 2nd trimester. Increased in T21
Why do the 10-14 week first trimester scan
Dating, measure NT, check placenta location number of babies
Nt will detect what % T21
75-85%
% Chr abn pregnancies with NT under 3.5mm
0.2%
DS with no nasal bone
Absent nasal bone detect60-70% DS
% Chr abnormal fetus that have holoprosencephaly
30%
What is associated with holoprosencephaly on scan
T13, T18 and 7q36 deln
Abscan in T21
Nuchal oedema, heart, duodenal atresia, but only 75% t21 have major anomalies on uss
Abscan for T13
Holoprosencephaly, iugr, heart, renal,echo genie large kidney, eximohals post axial polydactyly
Abscan for triploidy
Diandry: molar prey rare +20 weeks, digyny: thin placenta, severe iugr, vebtriculomegaly, syndactyly
Abscan t18
Strawberry head, cpc, absent corpus collosum, cleft, iugr, overlap fingers , exomohalos diaphragmatic hernia
Abscan turners
Cystic hygroma, oedema, horseshoe kidney, pleural effusion ascites heart
Abscan PK
Diaphragmatic hernia , shirt limb, abn hands and feet
Abscan Roberts syndrome
Severe limb shortening (upper) oligodactyly thumb aplasia cystic kidney
Abscan mosaic T2
Absent gall bladder talipes renal cyst omphalocele
% woman who screen as high risk
3%
