Sonography & Anomaly testing

Question 1

What are the routine ultrasound scans done in pregnancy?

Answer 1

Early USS at 10-13+6w

Anomaly scan at 18-20+6w

Question 2

What is the earliest Early pregnancy USS you can do?

Indications [4]

Answer 2

<11w
Not done routinely
Ind: hyperemesis gravidarum, bleeding or pain

Question 3

What changes can you see at:

4.5w, 5w, 6w

Answer 3

o 4.5w: womb thickening and gestational sac
o 5w: yolk sac
o 6w: heart beat

Question 4

Early USS @ 10-13+6w

Purpose [4]

Answer 4

Ensures viable pregnancy
Detects multiple pregnancy
Identifies if incompatible with life
Calculation of GA, EDD

Question 5

Early USS @ 10-13+6w
What are anomalies that are incompatible with life? [4]
How to calculate GA?

Answer 5

T13, T18
Anencephaly
Bilateral renal agenesis
Some major cardiac malformations

GA is calculated using fetal pole > GA correlates with Crown Rump Length

Question 6

Anomaly scan @ 18-20+6w
Purpose [7]
Limitations [3]

Answer 6

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

Question 7

Anomaly scan @ 18-20+6w

• Skull shape, brain [3]
• Spine [1]
• Abdomen [5]
• Arms and legs [1]
• Heart [2]
• Face and lips [1]

Answer 7

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

Question 8

Other sonography scans that can be done

Answer 8

Fetal ECHO
Fetal growth scans
Doppler US

Question 9

Fetal ECHO Indications [7]

Answer 9

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

Question 10

Fetal growth scans
Purpose [2]
Indications [2]

Answer 10

Requires accurate GA, AC, HC, FL measurements
Calculates estimated fetal weight, liquor volume (AFI)
Determines overall pattern of growth

Indications: SGA, LGA

Question 11

Dopple US - 3 types

Answer 11

Uterine artery
Umbilical artery
Fetal vessel

Question 12

Uterine artery doppler
What does it measure?
Clinical significance [2]
When is it carried out?

Answer 12

Measures resistance within placenta
If high resistance this indicates a risk of PET, IUGR
Carried out at 23w

Question 13

Umbilical artery doppler
What does it measure?
Clinical significance [2]
Indications

Answer 13

Measures resistance within placenta
High resistance indicates placental failure, risk of IUD, absent/reversed end diastolic flow indicates delivery by LSCS
Indicated in SGA

Question 14

Fetal vessel doppler
2 types
When is it carried out?

Answer 14

MCA doppler and Ductus Arteriosus doppler
Both used at time of delivery in <32w
MCA used to detect fetal anemia

Question 15

Fetal anomaly testing components
Down syndrome [2]
NTD [4]

Answer 15

Down syndrome: screening tests and prenatal diagnosis tests

NTD:

• 1st trimester USS
• 2nd trimester biochemical screening
• Anomaly scan

Question 16

Down syndrome testing Screening tests [2]

Answer 16

o 11-13+6w: combined test
1. Serum: B-HCG + PAPP-A
2. USS: fetal nuchal translucency
o 15-20w: triple or quadruple test

Question 17

What does PAPP-A stand for?
What is PAPP-A?
Causes of low PAPP-A levels? [4]

Answer 17

Pregnancy associated plasma protein A
Glycoprotein produced by placenta
Causes of low PAPP-A levels:
T18, T21
Pre-eclampsia
Preterm delivery
Fetal demise, IUGR

Question 18

What result in serum testing would you expect if baby had Down syndrome?

Answer 18

High B-HCG
Low PAPP-A
High risk if <1 in 150 chance

Question 19

Triple test components and expected result

Quadruple test components and expected results

Answer 19

 Triple test: alpha-fetoprotein (AFP) (low), unconjugated oestriol, beta HCG (high)
 Quadruple test: AFP, unconjugated oestriol, beta HCG, inhibin A (high)

Question 20

Prenatal diagnosis in Down syndrome testing:
Chorionic villus sampling define
Limitations [4]
Contraindication [1]

Answer 20

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

Question 21

Prenatal diagnosis in Down syndrome testing:
Amniocentesis define
Requirement
Risk

Answer 21

Sample of amniotic fluid
Anti-D required in all RH-ve women
1% risk of fetal loss at 16w gestation

Question 22

Compare the times at which both prenatal investigations can be done [2]

Answer 22

Amniocentesis: Carried out 15w and onwards
CVS: 10-14w

Question 23

Neural tube defects testing
Indications
What is a positive result on 2nd trimester biochemical screening?

Answer 23

Indication: past history or family history of NTD

Maternal Alpha fetoprotein measured: >2.0 MoM warrants further investigation

Question 24

NTD testing - anomaly scan what would be the findings of positive? [2]

Answer 24

Lemon shaped skull

Curved cerebellum

Question 25

Alpha fetoprotein causes of
Increased [4]
Decreased [3]

Answer 25

Causes of increased AFP:

• Open NTD
• Abdominal wall defects
• Multiple pregnancy
• Incorrect estimation of GA

Decreased AFP:

• Down syndrome
• T18
• Maternal DM

Question 26

What is non-invasive prenatal testing (NIPT)

Answer 26

Take maternal blood and detect fetal cell free DNA then look for Trisomies.

However its not on NHS and even if high risk, invasive testing still needs to confirm

Question 27

First sign of pregnancy on USS

Answer 27

Thickening of lining of uterus