ICRI GUIDELINES 2022
2ND TRIMESTER LEVEL 2 / TARGETED IMAGING FOR FETAL ANOMALIES (TIFFA)
SEPTEMBER 2022
ICRI SUBSPECIALITY GROUP ON FETAL RADIOLOGY
DR.SRINIVAS SHENTAR, DR.RIJO MATHEW, DR.ALPANA JOSHI, DR.SMITA
MANCHANDA, DR.NAMRATHA PURUSHOTAMAN.
TYPES OF 2ND TRIMESTER SCANS
1. A basic scan (called Basic Anomaly Scan or Level 1 Anomaly Scan).
2. Detailed scan (called TIFFA or Targeted Imaging for Fetal Anomalies or Level
2 Anomaly Scan).
WHERE CAN IT BE DONE:
Centres approved by PC-PNDT.
DIFFERENCE BETWEEN THE SCANS
1. Basic Anomaly Scan – An overview of the gross fetal structure as per
protocol. It is accepted that many minor findings may not be picked up in this
scan.
2. TIFFA (Targeted Imaging for Fetal Anomalies) – It is a more detailed scan
with clinical background (if available / relevant), extended biometry, Doppler
as per protocol, clinical correlation if required, with recommendations.
However, it does not include detailed Fetal Echocardiography. Though
detection rate increases as compared with a basic scan, it is understood that
100% detection of fetal anomalies will not be possible and this has not been
achieved in any country in the world at present.
3. Fetal Echocardiography – This is a detailed study of the fetal heart as per
protocol* with documentation. It does not include other fetal parts and is an
exclusive study of the fetal heart. Though detection rate for cardiac anomalies
increases, it is understood that 100% detection of fetal cardiac anomalies is not
possible and this has not been achieved in any country in the world at present.
*protocol for TIFFA is described below.
4. Fetal neurosonography- This is a detailed study of the fetal brain as per
protocol* with documentation. It does not include other fetal parts and is an
exclusive study of the fetal brain. Even this study does not ensure 100%
detection of brain anomalies. There are false positive and false negative results
sometimes. MRI may be complimentary and reveal certain anomalies not seen
by ultrasound in some cases.
RATIONALE BEHIND DIFFERENT TYPES OF SCANS
Ideally, every pregnancy should have a detailed TIFFA with Fetal
Echocardiography. However, TIFFA and Fetal Echocardiography need high-end,
expensive Doppler machines, highly-trained personnel and more scan time per
case. As a result, that these scans are more expensive, more time consuming
and have limited availability. As such, it is not practically possible, at this point
in time, to offer these scans to every pregnancy case in the country. This is
especially true in rural areas and smaller towns which face problems like low-
end equipment, huge workload (associated with lack of time) and less
affordability.
Hence, a basic scan is usually offered. However, based on availability and
affordability, TIFFA can be offered. Fetal echocardiography is usually
recommended in specific circumstances (though there is no bar for referring
even low risk patients). The reason for this is that a significant number of fetal
cardiac abnormalities even occur in low risk population.
TIMING:
These scans are recommended between 18 to 24 weeks
If the patient has not undergone a scan in the 2nd trimester, even up to 28
weeks or later, if technically feasible.
Reason - many patients in our country present late in pregnancy and denying
them a detailed scan just because of an arbitrary “cut-off” date would not be
in the best interests of patients.
The ideal time for this scan would be around 22 weeks, though earlier it was
advised at 18-20 weeks. This is because of the change in the medical
termination law. Earlier, medical termination was allowed up to 20 weeks
which was the reason for the 18-20 weeks recommendation. Now that
terminations are allowed up to 24 weeks, it would be logical to suggest 22
weeks since the fetal organs would be bigger, brain better developed, etc.
These would allow more confident diagnosis, lesser false positives as well as
more true positive diagnosis. This timing would still allow 2 weeks buffer time
for any other investigations / decision making in case there are any anomalies.
LEVEL 2 ANOMALY SCAN / TIFFA
TIFFA is an acronym for “Targetted Imaging For Fetal Anomalies”.
AIMS OF DOING THIS SCAN:
Assess / Confirm number of fetuses.
Cardiac activity – Rate and rhythm.
To search for common abnormalities detectable by ultrasound. It is
understood that detection rate for many abnormalities is not 100%.
Dating pregnancy if no dating scan done earlier (less accurate than first
trimester).
Check interval growth if earlier scans done and available for review.
Assess placentation and liquor status.
Assess endocervical length (TVS if required).
Check for other uterine & adnexal pathologies like fibroids, ovarian cysts, etc.
Uterine artery Doppler.
EQUIPMENT :
Real-time ultrasound machine with Doppler.
Electronic callipers with biometry charts fed in the machine, eg. Hadlock
Growth Charts.
Depth, zoom, focus and gain settings.
Compounding, harmonics are desirable.
Convex transducer. Wide-band transducers preferable, not mandatory.
TVS transducer.
Linear transducer can be used.
ROUTE:
Trans-abdominal.
Trans-vaginal / trans-labial scans may be done for additional information, if
required.
PATIENT HISTORY:
A history of the patient with minimum of the following information is to be
recorded:
Height (in cms or feet, inches) / weight (in kgs)
Racial origin: South Asian / Caucasian / African / Mixed
Obstetric history: Gravida / para / live / abortions / ectopic pregnancies
Previous pregnancies: Pre-eclampsia
Birth weight
Premature or postmature deliveries
Conception: natural / ovulation induction / IVF
Cigarette smoking
Family history of pre-eclampsia
Interval from previous pregnancy
Medical history: chronic hypertension / diabetes / SLE / APS
Blood group (Rh factor):
MANDATORY SECTIONS:
Cranium – Trans-thalamic, trans-cerebellar and trans-ventricular.
Face – Mid-sagittal, orbits, ears, retronasal triangle and upper lips.
Spine – Midsagittal and axial sweep. Coronal sections optional.
Abdomen – Abdominal circumference section, urinary bladder, kidneys,
umbilical cord insertion, diaphragms (parasagittal).
Chest – Apical 4-chamber cardia, LVOT, RVOT, 3-vessel view, 3 vessel trachea
view, lungs.
Upper limbs – humerus, 2 bones in forearms, hands (fingers not mandatory).
Lower limbs – femur, 2 bones in leg, feet (counting toes not mandatory).
Placental location – if low lying, mention distance in mm from the internal os.
Liquor (assessed by subjective evaluation).
Cervical length.
Any other findings.
Uterine artery doppler.
Number of vessels in the cord.
MINIMUM LANDMARKS TO BE IDENTIFIED IN THE SECTIONS STUDIED:
Cranium – Mineralization of the skull,
midline echo,
cavum septum pellucidum (CSP),
thalami,
lateral ventricles,
lateral fissure,
cerebellum.
Face – Profile,
prenasal soft tissue,
upper lip,
retro-nasal triangle,
orbits and lens,
ears (presence of at least one external ear).
Spine – skin continuity over vertebrae.
Chest – uniform echogenicity of lungs,
4 chamber heart,
LVOT,
criss-cross of great vessels in real time,
3 vessel view,
3 vessel trachea view.
Abdomen – stomach approximate size (look of eye),
stomach position,
anterior abdominal wall,
kidneys,
urinary bladder,
both diaphragms with stomach below diaphragm (parasagittal).
Upper limbs – humerus,
2 bones in forearm,
carpus of the hands (counting fingers optional).
Lower limbs – femur,
2 bones in leg,
feet (counting toes optional).
MINIMUM BIOMETRY (EXTENDED BIOMETRY):
Measurements preferably in mm.
Cranium- BPD , HC, TCD, CM, NF, LV.
Face – NB, PNT, BOD, EAR.
Cardia – LVOT, RVOT.
Abdomen – AC, LK, RK.
Upper limb – HL, Radius.
Lower limb – FL, Tibia, Foot.
BPD = biparietal diameter, HC = head circumference, TCD = transcerebellar
diameter, CM = cisterna magna depth in midline, NF = nuchal fold thickness,
LV = lateral ventricle at level of atrium.
NB = nasal bone length, PNT = prenasal soft tissue thickness, BOD = binocular
distance, EAR = ear length.
LVOT = diameter of aorta at level of aortic valve, RVOT = diameter of
pulmonary artery at level of pulmonary valve.
AC = abdominal circumference, LK = left kidney, RK = right kidney.
HL = humerus length, radius = radius length.
FL = femur length, tibia = tibia length, foot = foot length.
Calculations:
PNT/NB ratio =
Calculated Gestational Age (CGA) = …...weeks…...days
EFW=…………. grams……PERCENTILE
Uterine artery Doppler: Left (PI) = Right (PI) = Mean PI =
Screen – positive / negative.
Use of Samrakshan calculator is encouraged, though not mandatory.
OTHERS:
Liquor – Subjective assessment, AFI / SDP if subjective assessment is abnormal
Placenta – Position and if low lying, distance from internal os.
INADEQUATE STUDY:
If a study is inadequate, it can be repeated after an interval of 2-3 weeks or
referred to a higher centre.
LIMITATIONS:
Dating may be grossly inaccurate after 24 weeks, and should not be used for
management decisions. If EDD has been mentioned in a previous scan, it
should not be reassigned in scans done later. However, the cEDD mentioned in
the earliest scan can be mentioned again.
All abnormalities cannot be detected by ultrasound. Many abnormalities may
develop later in pregnancy or even after birth (especially neurological) and
these may go undetected. Some anomalies may develop or progress later in
pregnancy, and this cannot be predicted.
Detection of chromosomal abnormalities is not possible by ultrasound and
presence of markers should not be interpreted / communicated as being
diagnostic. It should be communicated that markers for chromosomal
abnormalities are found even in normal fetuses, and they only indicate a
higher risk for chromosomal abnormalities. Conclusive proof is possible only
with chromosomal analysis which would entail doing invasive procedures.
Hence, risk analysis should be done in suspected cases and chromosomal
analysis recommended only in high risk cases. It should be remembered that
2nd trimester markers are less accurate than 1st trimester markers, hence, if a
1st trimester risk assessment has already been done, it is not necessary to do a
2nd trimester risk assessment. In case it is done, the a priori risk would be the
risk arrived at after 1st trimester screening and not just maternal age.
It is encouraged to educate patients regarding these.
Placental position changes as pregnancy progresses, and hence position in
early pregnancy should not be labelled as placenta previa. Distance of lower
edge of the placenta from the internal os should be mentioned where
required.
It is advisable to educate patients that even with a detailed scan like TIFFA,
only 60-65% of fetal abnormalities will be picked up by ultrasound. This will
prevent misunderstanding and disappointments. Patient expectations being
too high a major cause of unnecessary litigations.
REPRESENTATIVE STANDARD SECTIONS WITH LANDMARKS TO BE
IDENTIFIED:
Since image quality varies based on the thickness and composition of the
abdomen of the mother, it is understood that there will be limitations in the
diagnostic ability in some patients. It is advisable to mention in the report
technically difficult studies as the ability to diagnose abnormalities decreases in
such cases and anomalies may be missed even if a diligent search is made.
In case of anomalies / abnormalities, either the patient or patients’ attendant
and / or the referring doctor may be intimated if required.
If further tests or follow up scans are suggested, it is advisable to inform the
referring doctor and / or record this in the report.
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