Foetal Morphology Scan

<Imaging>   <Ultrasound>

<Index>

 

Definition

-  Routine second trimester ultrasound to assess foetus, placenta & liquor volume

 

Features

-  Performed between weeks 18-20/40

-  20 weeks is cut off for TOP due to foetal abnormalities wo committee approval

-  Considered part of routine antenatal care in pregnancy

 

Rationale

-  Routine US in second trimester of pregnancy

-  Part of second trimester US to

-  Establish number of foetuses

-  Deterine gestational age & normal growth

-  Exclude major structural abnormalities

-  Assess liquor volume (AFI)

 

Procedure

-  Second trimester US+

-  Head

-  HC, BPD, midline seperation, midline falx, cavum speti pellucidi, cerebellum, choroid plexus, cisterna magna

-  Lateral ventricles: ventriculomegaly

-  Neck: nuchal fold

-  Face, nose, chin

-  Nasal bone absence x40 likelihood of chromosomal abnormality

-  Lips, palate: cleft lip/palatte

-  Heart

-  Situs, position, orientation

-  4 chamber view

-  Intraventricular septum

-  +/- outflow tracts

-  Chest

-  +/- Lungs, mediastinum, aorta, IVC

-  Abdomen

-  Stomach: presence, size, situs

-  Kidneys

-  Bladder

-  Umbilical cord

-  Three vessel cord, SUA

-  Insertion site

-  Limbs

-  4 limbs, hands & feet

-  Spine

-  Transverse, coronal, sagital

-  +/- Gender

 

Results

-  AFI

-  Any structural defect = x25 chance of chromosomal abnormality

-  Detection Rates

-  40-50% Down Syndrome

-  90% Trisomy 13 & 18

-  90% spina bifida

-  99% anencephaly

-  25% Major congenital heart problems

-  60% diaphragmatic hernia

 

 

 

References

 

AIUM Practice Guideliens: Obstetric US, October 1 2007