Level II - Anomaly scan

Introduction

Level 2 Anomaly Scan or Targeted Imaging for Fetal Anomalies (TIFFA), is a detailed obstetric ultrasound examination, performed between 18 and 22 weeks of gestation.

• Timing: 18–22 weeks.

• Systematic Survey: A systematic, head-to-toe approach is crucial to ensure no structure is missed.

Components of the Examination

A. Fetal Biometry

Parameter	Required Axial Plane (	Measurement Technique
Biparietal Diameter (BPD) & Head Circumference (HC)	Trans-Thalamic Plane: Must include the Midline Falx, Cavum Septum Pellucidum (CSP), and Thalami.	BPD: Outer skull to inner skull (Outer-to-Inner). HC: Ellipse trace of the outer skull perimeter.
Abdominal Circumference (AC)	Transverse Abdominal Plane: Must include the Stomach Bubble (on the fetal left) and the Umbilical Vein uniting with the portal vein (Hockey Stick Sign).	Ellipse trace of the outer skin line. Avoid including kidneys or heart.
Femur Length (FL)	Longitudinal View: True long-axis of the bone.	Measure the ossified diaphysis from end to end, excluding the cartilaginous epiphyses.

Detailed Anatomical Survey (Head-to-Toe)

A. Central Nervous System (CNS)

1. Trans-Thalamic Plane: Midline Falx, Thalami, and the normal appearance of the CSP.

   
   

2. Trans-Ventricular Plane: Angled slightly superiorly to measure the lateral ventricles.

   
   

3. The Atrium (Posterior Horn) should be measured at the glomus of the choroid plexus; a diameter >10 mm suggests ventriculomegaly.

   
   

4. Trans-Cerebellar Plane (Posterior Fossa): Measure the Transcerebellar Diameter (TCD) and the size of the Cisterna Magna (normally 2−10 mm).

   
   

5. Check the shape of the cerebellum ("Banana Sign") and the frontal bone ("Lemon Sign") as screening signs for Spina Bifida.

B. Face, Neck, and Spine

• Face: 

  • Mid-sagittal profile to assess the chin (micrognathia) and confirm the presence of the Nasal Bone.

  • Coronal view to evaluate the integrity of the upper lip and alveolar ridge to rule out Cleft Lip/Palate.

    
    

• Neck:

  • Rule out umbilical cord around the neck.

    
    

• Spine: 

  • Axial sweep from cervical to sacral spine: for closure of the vertebral arches and the integrity of the overlying skin line (Spina Bifida).

  • Sagittal and coronal views confirm bony alignment.

C. Thorax and Heart

• Lungs and Diaphragm: Assess uniform echogenicity of the lungs. Confirm the integrity of the diaphragm by noting the stomach is inferior to it (ruling out Congenital Diaphragmatic Hernia).

• Fetal Echocardiography (Screening Views):

  • Four-Chamber View (4CV): The hallmark view. Confirm cardiac situs (levocardia), check heart size (occupying ≈1/3 of the chest area), and ensure both atria and ventricles are approximately equal in size. Evaluate the insertion of the atrioventricular valves.

  • Outflow Tracts (LVOT/RVOT): Obtain views demonstrating the aorta leaving the left ventricle and the pulmonary artery leaving the right ventricle.

  • Three-Vessel and Trachea View (3VTV): A superior transverse view showing the parallel arrangement of the pulmonary artery, aorta, and superior vena cava.

D. Abdomen and Pelvis

• Abdominal Wall: Inspect the umbilical cord insertion site closely for wall defects like Omphalocele or Gastroschisis.

• Situs: Confirm the stomach bubble is on the left.

• Renal System: Identify both kidneys. Check for the presence of the urinary bladder. Measure the renal pelvis (A-P diameter ≥4 mm is significant for pyelectasis, a common soft marker).

• Bowel: Assess for increased echogenicity (Hyperechoic Bowel), which may be a soft marker or indicate pathology.

E. Extremities and Musculoskeletal System

• Long Bones: Visualize the humerus, radius, ulna, femur, tibia, and fibula bilaterally. Look for shortening or bowing, suggestive of skeletal dysplasia.

• Hands and Feet: Confirm the presence of hands and feet. Assess the position of the feet relative to the leg to rule out clubfoot (talipes). Gross visualization of the digits is often attempted but not always mandatory.