What is it : Also call 2nd trimester anomaly scan, target imaging for fetal anomaly scan (TIFFA), and Anatomy scan. Anomaly scan is type of ultrasound scan which detects presence of any abnormalities in the fetuses.
Role of ultrasound: Since the early 1970s, ultrasound devices have been serving modern medicine and they have become an indispensable part of pregnancy monitoring. Parallel to the advances in computer technology and developments in industry, the image quality of ultrasound devices has also improved. The reliability of ultrasound has long been known. It helps Direct visualization of defects such as Anencephaly, visualization of pathology due to defects such as dilated stomach and duodenum (deudenal atresia) , increased nuchal fold and short femur ( down syndrome) , ultrasonic marker of chromosomal abnormalities , guide to obtain fetal tissue, such as amniocentesis, fetoscopy, chronic villous biopsy, cordocentesis
Importance: The screening for congenital abnormalities is one of the most important ultrasound scans during pregnancy. At this stage of pregnancy the fetus has all organs developed and it faces the growth and maturing period. It can detect congenital malformation, and can decide to termination of pregnancy or not and or fetal therapy. It can show gestational age , number of pregnancy, fetal measurement of growth, aneuploidy screening, viability, and assess chorionicity and amnionicity.
The fetus already opens its mouth and swallows and breaths amniotic fluid, feeling its smell and taste. The inner ear of the fetus has already fully developed, so that it can hear the sounds coming from the uterus: heartbeat of the mother, breathing murmur of lungs, movement of gut. At the same time it is not yet able to differentiate the sounds coming from outside the utero, e.g. father’s speech. The child’s skin is covered with little hairs and fetal ointment which protect it against the macerating impact of amniotic fluid. The fetus has already eyebrows and eyelids, but eyes are still covered by embryonic film, thus it cannot still open its eyes. The fetus has no hair or lashes, but nails are already forming on toe and fingertips. The size of the fetal heart already corresponds to the size of one euro coin and the heart beats 120-180 times a minute. This is twice as fast as the mother’s, i.e. the heartbeat of the mother and father together.
Core aims and objective of the anomaly scan
– Identifications of lethal abnormalities
– To be able to offer a choice about whether or not continue with pregnancy in which the baby is abnormal
– Identifications of abnormalities for which there may be intrauterine treatments
– To be able to plan appropriate management of the pregnancy and delivery
– Identifications of abnormalities amenable to immediate neonatal treatment
– To enable the development of care pathways for individual women.
For serious abnormalities there are four possible pathways:
- Incompatibilities with prolong life
- Association with serious morbidity
- Amenability to postnatal treatment with relatively low morbidity
- Antenatal treatment
When is appropriate time to do Anomaly Scan ?
1st trimester ultrasound : Between 11-14 weeks of pregnancy
To end of 1st trimester, gross fetal anomalies
2nd trimester: between 18 – 22 weeks of pregnancy
Morphologic assessment at 18-22 weeks of pregnancy using 2D, 3D and 4 D USG
The following structures should be visualized at a routine second trimester morphology ultrasound.
- Fetal skull: integrity and shape
- Fetal brain
- ventricles and choroid plexus
- cavum septum pellucidum
- posterior fossa, including measurements of transcerebellar diameter and cisterna magna
- nuchal fold thickness
- Profile and nasal bone
- Orbits and lenses
- Upper lip and palate
Fetal heart and chest
- Fetal heart rate and rhythm
- Cardiac situs
- Four chamber view
- Outflow tract views
- Aortic and ductal arches
- Diaphragm and lungs
- Stomach (including situs)
- Kidneys and renal arteries
- Abdominal wall
- Umbilical cord insertion
- Bladder and umbilical arteries
- Presacral space
- Fetal gender
Fetal musculoskeletal system
- transverse, longitudinal +/- coronal views and skin line
- Upper limb
- humera, including humeral length (HL)
- radius/ulna: both sides
- fingers and thumbs, including hand opening
- Lower limb
- both femora, including femoral length (FL) as part of biometric assessment
- both tibia/fibula: saggital views to demonstrate orientation of the ankles to screen for talipes.
- both feet
- Fetal lie
- Cervical length
- distance to cervix
- Liquor volume
- Umbilical cord including the number of cord vessels and evaluation of knots
What is 3D/4D ultrasound?
Diagnosis of fetal anomalies is important in detecting fetal/maternal problems that may occur during and after pregnancy. Therefore fetal imaging is great importance for obstetricians. The efficacy of 2D, 3D and 4D ultrasound in diagnosis has been evaluated by several studies and the use of 4D ultrasound in routine practice has begun to be investigated.
In recent years, the three –dimensional (3D)/four-dimensional (4D) ultrasound has reached a worldwide and nowadays it takes part of all obstetric gynecologic diagnostic areas. The image quality of the state-of-the-art technology, 4D ultrasound, is significantly better than the standard 2 dimensional (2D) ultrasound, in a way that the details of the tissue are almost as distinguishable as the Magnetic Resonance (MR) images.
This article “Anomaly scan” is written by Dr Arun K Yada, MBBS, MD Radiologist (Tongji University, Shanghai, China). Dr Arun can be contacted at Precious Ultrasound & Doppler Center Pvt Ltd, Thapathali, Kathmandu, Nepal, Tel: 01-4101753, 9849156227.
Anomaly scan images/figures included in the article:
|Figure 1: 2 D Normal sagittal image||Figure 2 : 2D fetal mid sagittal Normal facial profile|
|Figure 3: 3D/4D Normal facial images||Figure 4: Normal Fetal face by 3D/4D|
|Figure 5: Normal 3 D images of 14 weeks of fetus||Figure 6: 3D images of fetal cleft lip and Palate|
|Figure 7: 2D and 3D images of fetal face with cleft lips and Palate||Figure 8: Club Foot as shown in above|
|Figure 9: 2D Image: Neural Tube Defect||Figure 10: A- 2D, B- 3D Coronal, C- T1MRI images : shows absence of fetal spinal caudal at T12 (arrow)|
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