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S
imões
and
B
ernardo
4
R
ev
A
ssoc
M
ed
B
ras
2017; 63(1):4-6
GUIDELINES IN FOCUS
What is the role of routine ultrasonography performed in the first
trimester of low-risk pregnancy?
Q
ual
é
o
papel
da
ultrassonografia
de
rotina
realizada
no
primeiro
trimestre
em
gestações
de
baixo
risco
?
Authorship:
Brazilian Medical Association (AMB)
Participants:
Ricardo Simões
1
, Wanderley M. Bernardo
1
Final draft:
April 2016
1
Programa Diretrizes, Brazilian Medical Association (AMB)
http://dx.doi.org/10.1590/1806-9282.63.01.4The Guidelines Project, an initiative of the Brazilian Medical Association, aims to combine information from the medical field in order to standardize
procedures to assist the reasoning and decision-making of doctors.
The information provided through this project must be assessed and criticized by the physician responsible for the conduct that will be adopted, depending
on the conditions and the clinical status of each patient.
S
tructured
question
The clinical question is structured according to the PICO
components: P (Patient), I (Intervention), C (Comparison),
O (Outcome).
•
•
P:
Low-risk pregnancy (first trimester)
•
•
I:
Ultrasonography
•
•
C:
•
•
O:
B
ases
of
scientific
data
consulted
The scientific database searched was PubMed-Medline. A
manual search of the references of reviews (narrative or
systematic) was also performed.
S
trategies
for
search
of
evidence
PubMed-Medline
Strategy:
(Pregnancy Trimester, First OR First Trimester OR Phases,
Early Placental OR Pregnancy Trimesters, First OR First Pregnancy
Trimester OR Pregnancies, First Trimester) AND (Ultrasonography
OR Echography OR Ultrasonic Diagnoses). N=838
R
esults
of
the
evidence
selected
The evidence was assessed according to the Oxford clas-
sification, which establishes the strength of the evidence
based on the study design chosen.
D
iscussion
Ultrasonography allows the evaluation of the fetal mor-
phology and biometric data, the examination of the fetal
anatomy and the detection of major congenital defects,
as well as subtle markers that signal the possibility of
chromosomal abnormalities and genetic syndromes.
Until a few years ago, early ultrasonography aimed to
identify the number of fetuses, to verify chorionicity in
the case of multiple pregnancies, and to date the preg-
nancy. In recent years, however, with improved technol-
ogy providing images with better resolution, as well as
access to ultrasound examinations for a greater number
of pregnant women, early identification of embryo-fetal
defects has been favored. The objective of this review was
to evaluate the contribution of ultrasound performed
in the first trimester (between weeks 11 and 14) in low-
-risk pregnancies (except in the situations listed in Table
1). Aspects assessed include determining gestational age,
characterizing multiple pregnancies, and evaluating the
fetal anatomy. With regard to the diagnosis of malforma-
tions, it is possible to detect structural abnormalities
and genetic syndromes.
Verification of gestational age
Calculating gestational age continues to be an extremely
important measure in prenatal follow-up and reproduc-
tive research, allowing appropriate assessment of fetal
development. Inaccuracies are inherent to the ultrasound
imaging method and often observed, especially measure-
ment errors and the biological variability of the fetus.
Numerous studies have revealed that the estimated ges-
tational age obtained from ultrasound proved to be su-
perior to that obtained using the date of the first day of
the last menstrual cycle (LMP), predicting even more
safely the probable date of delivery.
2-4
(
B
) This fact stems
mainly from the difficulty many women have in inform-