Obs - congenital abnormalities Flashcards
what are the characteriistics of a good screening test?
Cheap
High sensitivity
o Proportion of subjects with the condition who screen positive for the condition
High specificity
o Proportion of subjects without the condition who are classified as screen negative
Safe
Acceptable diagnostic test for the disorder for which it is screening
what are the methods of prenatal testing in the mother?
Maternal blood test
Ultrasound
FMRI
3D/4D US
AMniocentesis
CVS
PGD - pregenetic diagnosis
what does increased maternal blood afp tell us?
neural tube defects: increased afp
gastrochisis : increased afp
not used much - US used instead
what is the nuchal translucency?
normal range?
fluid-filled subcutaneous space identified at the back of the fetal neck during the late first trimester and early second trimester
approx less than 3.5mm
all abnormlaities are picked up on the anomaly scan at 20 weeks. true/false
false
some may develop later eg cardiac abnormality
use of fmri in pregnancy?
intracranial lesions
soft tissue differentiation
how would one ivx prenatally for cmv, toxoplasmosis, and inherited conditions eg thalassaemia?
Amniocentesis
risks of amniocentesis?
1% miscarriage chance
infection
how can chromosomal abnormalities be tested for?
Amniocentesis + FISH/PCR
CVS - (biopsy of the trophoblast) + FISH/PCR
- tests for AD/AR conditions
- higgher miscarriage rate tham amnio
what are the conditoins for pre implantation genetic diagnosis to be done?
What can be tested for?
need to do IVF
sex linked, trismoies, AD/AR
What are the trismoies and associated syndromes?
21, 18, 13
D, E, P
downs, Edwards, patau
what causes trisomies?
non-dysjunction during meiosis
6% balanced chromosal translocation
what are the rsik factors for downs syndrome ?
maternal, US, bloods
Maternal:
increased age, previous affected baby
Ultrasound:
thickened n translucency,
Absent/short nasal bone
Tricuspid regurgitation
Bloods: Low PAPP-A (1st tri) Low AFP (1st/2nd) Low oestriol (2nd) High inhibin (2nd) High B-hCG (1st/2nd)
what are diagnostic test for trismoies?
amniocentesis and cvs
so everything listed in risk factor is just rf, not decisive.
what tests are done fore screening on downs syndrome?
1. COMBINED TEST: risk from maternal age PAPP-A - blood test B-hCG - blood test Nuchal scan - nuchal translucency ( 11-13+6 weeks)
2. Triple test - done if screening was done late (>14wks) o AFP o hCG o Oestriol - done at 16 weeks. less accurate
Amniocentesis, CVS - daignostic tests - not screening
how does anencephaly present
Absence of cranium - parts fo brain, skull and scalp
Frog Eye appearance on USS
Incompatible with life
what can be done about NTD in utero?
open surgery can reduce disability
how do cardiac abnormlaities present?
rx?
50% enlarged nuchal translucency
rx: in utero rx of arrthymia (with drugs).
valvoplasty - aortic stenosis
name some abdominal structural abnormalities? - defects in abdominal wall
rx?
Exomphalos ? Omphalocele - extrusion of abdominal contents but remains in a sac. good prognosis
Gastrochissis - free loops of bowel in amniotic cavity. good prognosis. surgery post fatally
what are the complications of pleural effusions in pregnancy?
hydros fetalis
list some causes of hydrops fetalis?
Non immune: Twin–twin transfusion syndrome Chromosomal abnormalities Structural abnormalities - e.g. pleural effusions Cardiac abnormalities or arrhythmias Anaemia - causing cardiac failure
Immune:
Anaemia + Haemolysis - Alpha thalasaemia, parvovirus
Result of rhesus disease or ABO mismatch
treatment for hydrops?
depends on cause:
anaemia - blood transfusion
pleural effusion - pleuroamniotic shunt
Twin–twin transfusion syndrome - laser ablation
otherwise untreatable!
the double bubble sign is indicative of?
dilated upper stomach
often seen in Down’s
GI structural defects often lead to?
Polyhydramnios
what is the most common cause of hydrops in early pregnancy?
chromosomal abnormalities particularly tri 21 - Down’s
how would you investigate suspectef hydrops?
1st line:
US
Echocardiography
MCA doppler
Others:
Maternal blood - kleihauer, infection
Fetal blood sampling if anaemia is suspected
Amniocentesis - karyotype, infectious causes
name a medical therapy for polyhrdamnios?
NSAIDs
