Sonography & Anomaly testing Flashcards
What are the routine ultrasound scans done in pregnancy?
Early USS at 10-13+6w
Anomaly scan at 18-20+6w
What is the earliest Early pregnancy USS you can do?
Indications [4]
<11w
Not done routinely
Ind: hyperemesis gravidarum, bleeding or pain
What changes can you see at:
4.5w, 5w, 6w
o 4.5w: womb thickening and gestational sac
o 5w: yolk sac
o 6w: heart beat
Early USS @ 10-13+6w
Purpose [4]
Ensures viable pregnancy
Detects multiple pregnancy
Identifies if incompatible with life
Calculation of GA, EDD
Early USS @ 10-13+6w
What are anomalies that are incompatible with life? [4]
How to calculate GA?
T13, T18
Anencephaly
Bilateral renal agenesis
Some major cardiac malformations
GA is calculated using fetal pole > GA correlates with Crown Rump Length
Anomaly scan @ 18-20+6w
Purpose [7]
Limitations [3]
Purpose: systematic structural review to identify problems requiring intervention
- Skull shape, brain
- Spine
- Abdomen
- Arms and legs
- Heart
- Face and lips
Limitations
- Poor predictor of chromosomal abnormalities
- Fetal positioning
- High maternal BMI
Anomaly scan @ 18-20+6w
- Skull shape, brain [3]
- Spine [1]
- Abdomen [5]
- Arms and legs [1]
- Heart [2]
- Face and lips [1]
o Skull shape and internal structures: cerebellum, ventricular size, nuchal fold
o Spine: NTD
o Abdomen: Gastrochisis, exomphalos, duodenal atresia (double bubble sign), diaphragmatic hernia, hydronephrosis
o Arms and legs: 3 bones and a hand or a foot
o Heart: Congenital heart defects, diaphragmatic hernia
o Face and lips: Cleft lip and palate
Other sonography scans that can be done
Fetal ECHO
Fetal growth scans
Doppler US
Fetal ECHO Indications [7]
Generally if high risk of fetal cardiac abormality PHx, FHx Nuchal translucency >3.5mm Suspected abnormality Drugs in pregnancy (lithium) Monochorionic twins Pre-existing DM
Fetal growth scans
Purpose [2]
Indications [2]
Requires accurate GA, AC, HC, FL measurements
Calculates estimated fetal weight, liquor volume (AFI)
Determines overall pattern of growth
Indications: SGA, LGA
Dopple US - 3 types
Uterine artery
Umbilical artery
Fetal vessel
Uterine artery doppler
What does it measure?
Clinical significance [2]
When is it carried out?
Measures resistance within placenta
If high resistance this indicates a risk of PET, IUGR
Carried out at 23w
Umbilical artery doppler
What does it measure?
Clinical significance [2]
Indications
Measures resistance within placenta
High resistance indicates placental failure, risk of IUD, absent/reversed end diastolic flow indicates delivery by LSCS
Indicated in SGA
Fetal vessel doppler
2 types
When is it carried out?
MCA doppler and Ductus Arteriosus doppler
Both used at time of delivery in <32w
MCA used to detect fetal anemia
Fetal anomaly testing components
Down syndrome [2]
NTD [4]
Down syndrome: screening tests and prenatal diagnosis tests
NTD:
- 1st trimester USS
- 2nd trimester biochemical screening
- Anomaly scan
Down syndrome testing Screening tests [2]
o 11-13+6w: combined test
1. Serum: B-HCG + PAPP-A
2. USS: fetal nuchal translucency
o 15-20w: triple or quadruple test
What does PAPP-A stand for?
What is PAPP-A?
Causes of low PAPP-A levels? [4]
Pregnancy associated plasma protein A Glycoprotein produced by placenta Causes of low PAPP-A levels: T18, T21 Pre-eclampsia Preterm delivery Fetal demise, IUGR
What result in serum testing would you expect if baby had Down syndrome?
High B-HCG
Low PAPP-A
High risk if <1 in 150 chance
Triple test components and expected result
Quadruple test components and expected results
Triple test: alpha-fetoprotein (AFP) (low), unconjugated oestriol, beta HCG (high)
Quadruple test: AFP, unconjugated oestriol, beta HCG, inhibin A (high)
Prenatal diagnosis in Down syndrome testing:
Chorionic villus sampling define
Limitations [4]
Contraindication [1]
Placenta sampled trans-abdominally with continuous US guidance
- 1-2% risk of fetal loss
- Increased risk of BBV
- Contamination by maternal cells
- Placental mosaicism - false positives and negatives
CI: dichorionic multiple pregnancy
Prenatal diagnosis in Down syndrome testing:
Amniocentesis define
Requirement
Risk
Sample of amniotic fluid
Anti-D required in all RH-ve women
1% risk of fetal loss at 16w gestation
Compare the times at which both prenatal investigations can be done [2]
Amniocentesis: Carried out 15w and onwards
CVS: 10-14w
Neural tube defects testing
Indications
What is a positive result on 2nd trimester biochemical screening?
Indication: past history or family history of NTD
Maternal Alpha fetoprotein measured: >2.0 MoM warrants further investigation
NTD testing - anomaly scan what would be the findings of positive? [2]
Lemon shaped skull
Curved cerebellum
