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SOGC CLINICAL PRACTICE GUIDELINE
Content of a Complete Routine Second
Trimester Obstetrical Ultrasound Examination
and Report
Abstract
Objective: To review the benefits of and requirements for a complete
second trimester ultrasound and the documentation needed.
Outcomes: A complete second trimester ultrasound provides
information about the number of fetuses, the gestational age, the
location of the placenta, and fetal and maternal anatomy.
Evidence: In the production of this document, the American Institute
of Ultrasound in Medicine’s “Practice Guideline for the
Performance of Obstetric Ultrasound Examinations,” the American
College of Obstetricians and Gynecologists’ practice bulletin,
“Ultrasound in Pregnancy,” and the Royal College of Obstetricians
and Gynaecologists’ Working Party Report, “Ultrasound
Screening” were reviewed. PubMed and the Cochrane Database
were searched using the words “routine second trimester
obstetrical ultrasound.”
Values: The evidence was evaluated using the guidelines developed
by the Canadian Task Force on Preventive Health Care.
Benefits, Harms, and Costs: A routine complete second trimester
ultrasound between 18 and 22 weeks and a complete ultrasound
report will provide the best opportunity to diagnose fetal anomalies
and to assist in the management of prenatal care. It will also
reduce the number of ultrasound examinations done during the
second trimester for completion of fetal anatomy survey. The costs
are those involved with the performance of obstetrical ultrasound.
Validation: This is a revision of previous guidelines; information
from other consensus reviews from medical publications has been
used.
Sponsors: The Society of Obstetricians and Gynaecologists of
Canada.
Recommendations
1. Pregnant women should be offered a routine second trimester
ultrasound between 18 and 22 weeks’ gestation. (II-2B)
2. Second trimester ultrasound should screen for the number of
fetuses, the gestational age, and the location of the placenta. (II-1A)
3. Second trimester ultrasound should screen for fetal anomalies. (II-2B)
J Obstet Gynaecol Can 2009;31(3):272–275
SECOND TRIMESTER ULTRASOUND
An ultrasound scan performed between 18 and
22 weeks’ gestation provides the pregnant woman and
her care provider with information about multiple aspects
of her pregnancy.1–4 The obstetrical ultrasound will inform
them of and/or confirm the number of fetuses present, the
gestational age, and the location of the placenta. It will pres-
ent an opportunity to diagnose congenital anomalies
and/or to detect soft markers of aneuploidy and to identify
maternal pelvic pathology.
The occurrence of twins undiagnosed at delivery is
extremely rare when women have received a second trimes-
ter ultrasound, and the likelihood of postdates induction
and intrauterine growth restriction significantly decreases.1
In the last two decades, the infant death rate from congenital
272 lMARCH JOGC MARS 2009
SOGC CLINICAL PRACTICE GUIDELINE
This clinical practice guideline has been reviewed by the
Diagnostic Imaging Committee and approved by the Executive
and Council of the Society of Obstetricians and Gynaecologists of
Canada.
The Society of Obstetricians and Gynaecologists of Canada
acknowledges advisory input from the Canadian Association of
Radiologists pertaining to imaging guidelines in the creation of this
document.
PRINCIPAL AUTHORS
Yvonne Cargill, MD, Ottawa ON
Lucie Morin, MD, Montreal QC
DIAGNOSTIC IMAGING COMMITTEE
Lucie Morin (Chair), MD, Montreal QC
Stephen Bly, PhD, Ottawa ON
Kimberly Butt, MD, Fredericton NB
Yvonne Cargill, MD, Ottawa ON
Nanette Denis, RDMS, CRGS, Saskatoon SK
Robert Gagnon, MD, Montreal QC
Marja Anne Hietala-Coyle, RN, Halifax NS
Kenneth Lim, MD, Vancouver BC
Annie Ouellet, MD, Sherbrooke QC
Marie-Hélène Racicot, MD, Montreal QC
Shia Salem, MD, Canadian Association of Radiologists, Toronto ON
Disclosure statements have been received from all members of
the committee.
Key Words: Routine second trimester ultrasound, ultrasound report
No. 223, March 2009 (Replaces No. 103, May 2001)
This document reflects emerging clinical and scientific advances on the date issued and is subject to change. The information
should not be construed as dictating an exclusive course of treatment or procedure to be followed. Local institutions can dictate
amendments to these opinions. They should be well documented if modified at the local level. None of these contents may be
reproduced in any form without prior written permission of the SOGC.
Content of a Complete Routine Second Trimester Obstetrical Ultrasound Examination and Report
MARCH JOGC MARS 2009 l273
Table 1. Content of a Complete Obstetrical Ultrasound Report
Category Required Information
Patient demographic
information •Patient name, second patient identifier (birth date, hospital identifier, health insurance number)
•Indication for consultation
•Requesting physician/caregiver (preferably with contact information)
•Starting date of last normal menstrual period (LNMP)
•Examination date
•Date of written report
•Name of interpreting physician
Number of fetuses and
indications of life
Presence of cardiac activity for each fetus
If multiple gestation: chorionicity and amnionicity should be reported
Biometry Should be reported all in millimetres or in centimetres along with equivalent estimated gestational age for:
•Biparietal diameter
•Head circumference
•Abdominal circumference
•Femur length
Should be reported in millimetres if abnormal
•Nuchal fold
•Cisterna magna
•Cerebellar diameter
•Lateral ventricle width
Fetal anatomy Should be reported as: normal OR abnormal (with details) OR not seen, with explanation
Should be reported for:
•Cranium
•Cerebral ventricles, cavum septi pellucidi, the midline falx, the choroid plexus
•Posterior fossa: cisterna magna, cerebellum
•Face: orbits, lips
•Spine
•Chest
•Cardiac four-chamber view
•Cardiac outflow tracts
•Heart axis
•Cardiac situs
•Stomach
•Bowel
•Kidneys
•Bladder
•Abdominal cord insertion
•Number of cord vessels
•Upper extremities and presence of hands
•Lower extremities and presence of feet
Amniotic fluid amount Should be reported as: normal OR increased OR decreased OR absent
Placenta •Position should be reported as well as relationship to the cervical os
Maternal anatomy uterus,
ovaries, cervix, bladder
Should be reported as:
•normal OR abnormal with details OR not seen
anomalies has decreased by 50% in infants born after
24 weeks.5This is likely at least partially related to early
diagnosis of congenital anomalies leading to either preg-
nancy termination or better neonatal care. Second trimester
diagnosis of congenital anomalies also provides the
opportunity for fetal therapy.
The literature includes descriptions of anatomical surveys
being performed before 18 weeks6but other studies have
repeatedly shown that more anomalies are diagnosed if the
scan is done after 18 weeks.1,2 A study done by Lantz and
Chisolm7found that in normal sized and in overweight
patients, a fetal anatomy survey for the detection of congen-
ital anomalies was more likely to be incomplete if per-
formed before 18 weeks than if performed at a later gesta-
tional age. In underweight patients, no difference was
found. The Royal College of Obstetricians and Gynaecolo-
gists recommends that the second trimester fetal anatomical
scan be performed between 20 and 23 weeks.8We recom-
mend that the second trimester ultrasound be performed
after 18 weeks and before 22 weeks’ gestation.9This will
allow pregnancy options if an anomaly is diagnosed and
avoid the added cost and unnecessary ultrasound exposure
of a repeat scan related to incomplete fetal anatomy survey.
This is a growing concern, as patients are increasingly likely to
have a high BMI.
When an ultrasound is performed at 18 to 22 weeks’ gesta-
tion, the maternal organs that should be screened are the
cervix, uterus, and adnexa. Any abnormality of these
structures should be documented.
The number of fetuses and the presence of cardiac activity
should be recorded. If a multiple gestation is diagnosed, the
chorionicity and amnionicity should be assessed and
documented.
The fetal biometric measurements should include at least
the following: biparietal diameter, head circumference,
abdominal circumference, and femur length. Absolute bio-
metric measurements with their estimated gestational age
should be documented and reported. A composite esti-
mated gestational age should also be reported, taking into
consideration measurement errors arising from abnormal
fetal body parts. Moreover, the gestational age/size should
be interpreted in correlation with any previous obstetrical
ultrasound if available. This will allow the care provider to
confirm if fetal growth has been appropriate. Due date
should not be adjusted if it has been established by an earlier
ultrasound.
Fetal Anatomy Survey to Be Performed
During a Complete Obstetrical Routine
Second Trimester Ultrasound
The standard fetal brain anatomical survey should
include an assessment and documentation of the following
anatomical landmarks: the shape of the fetal skull, the
cavum septi pellucidi, the midline falx, the choroid plexus,
the lateral cerebral ventricles, the cerebellum, the cisterna
magna, and the nuchal fold. The face should be scanned to
assess and document the orbits and lips.
In the thorax, the heart and lungs should be examined.
Examination of the fetal heart includes its relationship with
the chest (axis, size, and position) as well as the assessment
SOGC CLINICAL PRACTICE GUIDELINE
274 lMARCH JOGC MARS 2009
Table 2. Key to evidence statements and grading of recommendations, using the ranking of the
Canadian Task Force on Preventive Health Care
Quality of Evidence Assessment* Classification of Recommendations†
I: Evidence obtained from at least one properly randomized
controlled trial
II-1: Evidence from well-designed controlled trials without
randomization
II-2: Evidence from well-designed cohort (prospective or
retrospective) or case-control studies, preferably from more
than one centre or research group
II-3: Evidence obtained from comparisons between times or
places with or without the intervention. Dramatic results in
uncontrolled experiments (such as the results of treatment
with penicillin in the 1940s) could also be included in this
category
III: Opinions of respected authorities, based on clinical
experience, descriptive studies, or reports of expert
committees
A. There is good evidence to recommend the clinical preventive
action
B. There is fair evidence to recommend the clinical preventive
action
C. The existing evidence is conflicting and does not allow to
make a recommendation for or against use of the clinical
preventive action; however, other factors may influence
decision-making
D. There is fair evidence to recommend against the clinical
preventive action
E. There is good evidence to recommend against the clinical
preventive action
L. There is insufficient evidence (in quantity or quality) to make
a recommendation; however, other factors may influence
decision-making
*The quality of evidence reported in these guidelines has been adapted from The Evaluation of Evidence criteria described in the Canadian Task Force
on Preventive Health Care.11
†Recommendations included in these guidelines have been adapted from the Classification of Recommendations criteria described in the The Canadian
Task Force on Preventive Health Care.11
of the four chamber view and the relationships of the out-
flow tracts. The fetal cardiac motion should be observed
and a fetal heart rate recorded. The lungs should be exam-
ined for their echogenicity.
In the fetal abdomen, the anatomical survey should
include the position, presence, and situs of the stomach,
and visualization of the bowel, bladder, kidneys, cord inser-
tion, and number of cord vessels.
The fetal spine should be viewed throughout its length in
sagittal, coronal, and transverse planes if possible. The skin
line should be seen away from the uterine wall. This cannot
always be documented with still images.
An attempt should be made to assess the fetal genitalia.
All four limbs to the level of the hands and feet should be
visualized, and the presence of hands and feet should be
noted. Subjective assessment of bone size, shape, and den-
sity should be done. This cannot always be documented
with still images.
The placenta should be examined for position, appear-
ance, and presence or absence of abnormalities. The placen-
tal location and its relationship to the internal cervical os
should be assessed and documented.
A qualitative assessment of the amniotic fluid volume
should be made. It should be reported as normal, increased,
decreased, or absent.
Table 1 shows the recommended content of the report, but
other information may be provided in such consultations.
The ultrasound report should include all ultrasound infor-
mation necessary for appropriate management of the preg-
nancy. It needs to include the date the scan was performed
and the composite gestational age based on fetal biometric
measurements. The number and size of fetuses and the
measurements obtained to determine them should be
noted. If a structure was not seen, this should be reported,
along with the reason it was not seen. If fetal or maternal
abnormalities are reported, a differential diagnosis and,
when appropriate, a recommendation for further investiga-
tion should be provided. The report should comment on
any significant technical difficulty of the examination. The
final report should be easy to read.
It is acknowledged that even in the best of hands and cir-
cumstances, the 18–22 week scan has limitations and can-
not detect all fetal and maternal abnormalities.10
Any significant fetal or maternal abnormalities need to be
reported promptly to the caregiver. The communication
should be recorded in the patient’s file.
An ultrasound report summary should provide:
•Estimation of gestational age according to ultrasound if
this is the first obstetrical ultrasound, estimation of
gestational age according to last menstrual period dates,
and the expected date of confinement
•Appropriateness of the biometry, size, growth, and
estimated gestational age
•Summary of findings
•Differential diagnosis if indicated
•Recommendations for further investigations and
referral for tertiary centre assessment when necessary.
Recommendations
The evidence was evaluated using the guidelines developed
by the Canadian Task Force on Preventive Health Care
(Table 2).
1. Pregnant women should be offered a routine second
trimester ultrasound between 18 and 22 weeks’
gestation. (II-2B)
2. Second trimester ultrasound should screen for the
number of fetuses, the gestational age, and the location
of the placenta. (II-1A)
3. Second trimester ultrasound should screen for fetal
anomalies. (II-2B)
REFERENCES
1. Ecker JL, Green MF. Indications for diagnostic obstetrical ultrasound
examination. UpToDate [web site] Version 15.1, December 2006.
2. Neilson JP. Ultrasound for fetal assessment in early pregnancy (Review).
Cochrane Database Syst Rev 1998;Issue 4. Art. No.: CD000182. DOI:
10.1002/14651858.CD000182.
3. ACOG Committee on Practice Bulletins. ACOG Practice Bulletin, No. 58,
October 2008. Ultrasonography in pregnancy. Obstet Gynecol
2004;104(6):1449–58.
4. Seeds JW. The routine screening obstetrical ultrasound examination.
Clin Obstet Gynecol 1996;39(4):814–30.
5. Liu S, Joseph KS, Wen SW. Trends in fetal and infant deaths caused by
congenital anomalies. Semin Perinatol 2002;26(4):268–76.
6. Souka AP, Pilalis A, Kavalakis I, Antsaklis P, Papantoniou N, Mesogitis S,
et al. Screening for major structural abnormalities at the 11- to 14- week
ultrasound scan. Am J Obstet Gynecol 2006;194(2):393–6.
7. Lantz ME, Chisolm CA. The preferred timing of second-trimester
sonography based on maternal body mass index. J Ultrasound Med
2004;23(8):1019–22.
8. Whittle MJ, Chitty LS, Neilson JP, Shirley, Smith IM, Ville YG, et al.;
National Working Party, Royal College of Obstetricians and
Gynaecologists. Ultrasound Screening. Supplement to Ultrasound
Screening for Fetal Abnormalities. Royal College of Obstetricians and
Gynaecologists Working Party Report. July 2000. Available at:
http://www.rcog.org.uk/index.asp?PageID=1185. Accessed November 26, 2008.
9. Tjepkema M. Adult obesity in Canada: measured height and weight.
Statistics Canada, 82–620-MWE/2005001.
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Effect of prenatal ultrasound screening on perinatal outcome. RADIUS
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Force on Preventive Health Care. New grades for recommendations from
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Content of a Complete Routine Second Trimester Obstetrical Ultrasound Examination and Report
MARCH JOGC MARS 2009 l275
