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L15 - Congenital Abnormalities
RR = reoccurrence rate/relative Risk
…
L15 - Congenital Abnormalities
RR = reoccurrence rate/relative Risk
- Review the major fetal malformations
- Discuss the etiology of the major fetal malformations
- Assess the clinical ability to recognise fetal structural anomalies*
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Fetal Congenital Malformations
Definition
- Structural (how things are built) or textfunctional (how things work) anomalies - present at conception or occurs before the end of pregnancy - diagnosed before 6 years of age
WARDA Notifications
Collects data on development anomalies and cerebal palsy
- 1:20 fetus' born in WA have some kind of anomaly
- More common in males and multiple pregnancy (esp. monozygotic twins)
Statistics: 2014
- Musculo-skeletal
(26.6/1000 births) was the most common category of birth defects
Neural Tube Defects
(120 NSD pa)
Cranial end closes by day 24, and caudal end by day 26
- Reduction of occurrence over the years (voluntary folate fortification introduced in 1995)
- Folic Acid Supplementation, Abortion etc.
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Anencephaly
- failure to close cranial neuropore
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Spina Bifida
- failure to close caudal neuropore
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Chromosomal Abnormalities
Increasing incidence of Chrom-Abnormalities due to shifting demographic of maternal age. Women are having children later in life
Trisomy 21
Down's Syndrome
- This has the highest incidence of chromosomal mutation
- Progresive increase in incidence over the last 3 decades
- 55% of T21 occur in women >35 yo
- Most common cause of intellectual impairment in our community
- 3.2/1000 births
Chromosomal Features
Chr21 is the smallest Chromosome
- 95% of Tri 21's are caused by nondisjunction
- 4% due to unbalanced translocation (typ Chr14)
- 1% due to mosaicism (normal+abnormal chr's)
Non-Disjunction
- Failure of homologous chromosomes to separate in 1st meiotic division
- Failure of sister chromatids to separate in 2nd meiotic division
Phenotypic Features
1.CNS: Intellectual Disability (IQ50), Alzheimer's disease (high incidence), hypotonia (cardiac disease
- Facies: Flat facial profile, macroglossia, epicanthal folds, small ears
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Prenatal Diagnosis of Trisomy 21
- Prenatal screening for Trisomy 21 us now incorporated into antenatal care
Prenatal Screening Techniques
- Prenatal Diagnosis based on maternal age (CVS)
- Combined First Trimester Screening (80-90% detection - many women actively want to see pictures of the baby)
- Second Trimester screening (70-80%)
- Non-Invasive Prenatal Testing (Sensitivity ~99.5%, and false positive ~0.2%) (Not currently funded)
CFTS
- 11.3-14 weeks
- Ultra-sound searching for nuchal translucency
- High-False positive rate (4-5%)
- Participation is high
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NIPT
- Uses circulating free DNA with massively parallel sequencing/SNP (Amplification) array/microarray
Diagnostic for;
- Fetal gender in X-linked condItions
- Fetal Rhesus Typing
- Trisomy 21,13,18
- Other Genetic disorders
(Sex Chr's aneuploidy, microdeletion/duplication syndromes, monogenic disorders)
Reduced sensitivity for multiple pregnancy and in obese patients (breakdown of fat releases too much self-DNA)
Trisomy 18
Edward's Syndrome
- Incidence 1/5000 (30 pa WA)
Phenotypic Features
Multiple anomalies
Typically identified
on
- Ultrasound
- FTS
- NIPT
(NIPT > 98% Sensitivity (ppv= 50-80%))
Severe Structural Deformities
Trisomy 13
Patau's Syndrome
- Incidence 1/9000 (8 pa WA)
- Non-Invasive-Prenatal-Testing
(Sensitivity >97% (PPV 40-85%))
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Monsomy X
- Incidence 1/2500
Phenotypic Features
- Short Stature
- Early loss of Ovian Function
- Webbed Neck
- Lymphedema
- Cardiac Abnormalities
- Renal Abnormalities
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Cardiovascular Defects
Hypoplastic Left Heart Syndrome
- 90% of HLHS cases are isolated defects
- Incidence 0.2/1000 live births (8-9/year in Western Australia)
- Hypoplastic Left Ventricle
Tetralogy of Fallot
- Often associated with other conditions (eg. Di George syndrome)
- Incidence 0.3/1000 live births (11/year in Western Australia)
- Oxygenated and de-oxygenated blood mix
Transposition of the Great Arteries
- Often associated with other cardiac conditions (eg. VSD)
- Incidence 0.5/1000 live births (18/year in Western Australia)
- Aortic Artery connected to RV and Pulmonary Artery connected to LV, AA and PA are connected
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