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Prenatal Diagnosis - Coggle Diagram
Prenatal Diagnosis
Identification of Abnormalities
Ultrasound
Identifies Anatomic Malformations
Soft Findings
Minor anatomic variances, won't really affect life after birth too much. Just potential indicators for chromosomal abnormalities
Echogenic Bowel
Associated w/ cystic fibrosis less frequently
Associated w/ T 21
*Assessment of nasal bone -most important indication if nasal bone is absent of T 21
Thickening of Nucal fold
70-75% sensitive
Major structural malformations
When a structural defect is present there is a likelihood ratio of a karyotype abnormalities of 25
Bladder outlet obstruction
Frequency of karyotype abnormalities up to 25%
Consequences are renal dysplasia or pulmonary hypoplasia because of lack of amniotic fluid cuz that's mostly fetal urine
Duodenal Atresia
Frequency of karyotype abnormalities is 30-35%, T 21 most common
Abdominal Wall defects
Gastroschisis
No increase in frequency of karyotype disorders
Omphalocele
30-65% have karyotype abnormalities and/or other sytems abnormalities
Ventriculomegaly
May be associated w/ karyotype abnormalities
Causes CNS injury due to pressure on cerebral tissue
Holoprosencephaly
Most common abnormality of T 13
facial cleating is a common finding
Cardiac Defects
most common abnormalities are autosomal trisomies
VSD Ventricular Septal Defect (most common birth defect in US population
Hypoplastic LV (left ventricle is teeny-tiny, very dangerous)
Frequency of Karyotype abnormalities is 4-5%, significantly increases if extra cardiac abnormality also present
Cystic Hygroma
Frequency of abnormalities 50-70%
Most common abnormalities are 45X (turner's syndrome), and T 21
Molecular Genetics
Diagnostic tests for fetal aneuploidy
FISH
Results in ~1 day
Extremely specific to one chromosome(?)
CVS (Chorionic Villus Sampling)
Results in 3-7 business days
Ultrasound guided cell aspiration from placenta
Risk of loss: 0.5-1%
Technically difficult
10-12 weeks
earlier diagnosis
Aminocentesis
technically easier than CVS
15-16 weeks
Risk of loss 1:600-1:1000
ultrasound guided into amniotic fluid
Results in ~14 days
Fetal umbilical blood sampling (cordocentesis)
Need for rapid test results
After 20 weeks
Risk of loos 1%
Need to assessfetal anemia or infection
Ultrasound guided into umbilical vein (very difficult)
Results in ~3 days
Screening tests for fetal aneuploidy
First Trimester NT Screening
85% sensitivity of identifying T 21& T 18
Mother's serum analysis testing
bHCG
PAPP-A
Nucal translucency
Nasal bone
12-13 weeks
Can be used for T 21
Non-invasive Prenatal Screening (NIPS)
Positive tests should be confirmed by CVS or amniocentesis
10 weeks
screens for T13, 18, 21 sex chromosome abnormalities and major micro deletions
22q11.2 (DiGeorge Syndrome)
Sensivitity is 99% for T 21, slightly less for other normalities
Screening tests are:
Inexpensive
Non-invasive
Simple to administer
Highly sensitive
Really should be applied to the entire obstetric population for screenings to be most effective
Fetal Aneuploidy
Risk Factors
Structural fetal malformations
Positive family or personal history
Increased maternal age
Modifications to Obstetric Management
