Structured Abstract
Please note: In 2003, the CTF updated its Grades of
Recommendations to include an "I Recommendation" for situations where
insufficient evidence exists to allow a recommendation to be made.
(Formerly, these situations were captured under a "C
Recommendation".) This change is not retroactive, and all
"C Recommendations" made prior to 2003 have not been
reevaluated in light of the new "I" recommendation grade. For a
discussion of these recommendation grades, please link to the 2003 article in
the Canadian Medical Association Journal here.
Routine Prenatal Ultrasound Screening
Prepared by Geoffrey Anderson, MD, PhD, Intstitute for Clinical Evaluative
Sciences in Ontario (ICES), and Department of Health Administration, University
of Toronto
These recommendations were finalized by the Task Force in March 1994
Contents
Objective
To make recommendations for the use of a single or serial ultrasound examination
to estimate gestational age and to detect multiple pregnancies, malformation
or intrauterine growth retardation in pregnant Canadian women.
Burden
of Suffering
The goal of prenatal ultrasound screening is to reduce the rates of perinatal
illness and death from several causes, some of which (e.g. IUGR) are etiologically
non-specific. Therefore, the Task Force has reviewed the evidence
on the impact of prenatal ultrasound screening on measures of perinatal
illness and death rather than on its ability to detect specific abnormalities.
Options
A single ultrasound examination in the second trimester of pregnancy or
serial (usually 2) ultrasound examinations, 1 in the second trimester and
1 in the third trimester.
Outcomes
Perinatal mortality and illness, Apgar scores, decreased rates of induced
labour (better estimates of gestational age), earlier detection of twin
pregnancies, increased birth weight, and increased rates of therapeutic
abortions because of identification of fetal abnormalities.
Evidence
MEDLINE was searched up to October 1993 using the keywords ultrasonography
and randomized controlled trial. Bibliographies of retrieved articles were
also searched. Inclusion criteria were random allocation of pregnant women
to routine ultrasonography or no routine ultrasonography and outcomes of
perinatal illness or death were provided. The Cochrane Database of Systematic
Reviews was also searched. Recommendations were graded as:
|
A
|
Good evidence to support the recommendation that the condition
be specifically considered in a PHE. |
|
B
|
Fair evidence to support the recommendation that the condition
be specifically considered in a PHE. |
|
C
|
Poor evidence regarding inclusion or exclusion of the condition
in a PHE, but recommendations may be made on other grounds. |
|
D
|
Fair evidence to support the recommendation that the condition
be specifically excluded from consideration in a PHE. |
|
E
|
Good evidence to support the recommendation that the condition
be specifically excluded from consideration in a PHE. |
Quality of evidence was rated according to 5 levels:
|
I
|
Evidence from at least 1 properly randomized controlled
trial (RCT). |
|
II-1
|
Evidence from well-designed controlled trials without randomization. |
|
II-2
|
Evidence from well-designed cohort or case-control analytic
studies, preferably from more than 1 centre or research group. |
|
II-3
|
Evidence from comparisons between times or places with
or without the intervention. Dramatic results in uncontrolled experiments
could also be included here. |
|
III
|
Opinions of respected authorities, based on clinical experience,
descriptive studies or reports of expert committees. |
Values
The 13-member Task Force of experts in family medicine, geriatric medicine,
pediatrics, psychiatry and epidemiology used an evidence-based method for
evaluating the effectiveness of preventive health care interventions. Recommendations
were not based on cost-effectiveness of options. Patient preferences were
not discussed.
Background papers providing critical appraisal of the evidence and tentative
recommendations prepared by the chapter author were pre-circulated to the
members. Evidence for this topic was presented and deliberated upon in
1- to 2-day meetings from October 1993 to March 1994. Consensus was reached
on final recommendations.
Benefits,
Harms, and Costs
4 RCTs of single ultrasound examinations were examined. 3 showed no difference
in fetal mortality whereas the fourth one did although this difference
was no longer significant when the increased number of therapeutic abortions
for malformations were considered as deaths. The 4 studies did not differ
for Apgar scores or days in the special care nursery. 1 study showed that
women who had ultrasound examination had fewer inductions and a slight
increase in birth weight (42 g, P = 0.008), and another showed earlier
detection of twin pregnancies (100% detected before 21 weeks in the study
group vs 76% in the control group).
The 4 studies that assessed multiple ultrasound examinations showed
no differences in Apgar scores and perinatal deaths. 1 study showed fewer
hospital days and 1 showed more hospital days with ultrasonography.
Systematic reviews showed that a single ultrasound examination was associated
with early detection of twin pregnancies, decreased rates of induction,
increased birth weight in singleton pregnancies, increased rates of therapeutic
abortions because of fetal abnormalities and no differences in perinatal
mortality or Apgar scores. Late ultrasound examination showed no differences
for mortality, morbidity, or induction of labour. 1 meta-analysis showed
decreased perinatal mortality with a single ultrasound examination.
Recommendations
Recommendation grade [A, B, C, D, E] and level of evidence
[I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations
in support of individual recommendations are identified in the guideline
text.
-
There is fair evidence to include a single ultrasound examination in the
second trimester of pregnancy in women without clinical indications (normal
pregnancy) [B, I].
-
There is insufficient evidence to include or exclude serial ultrasound
examinations in the second and third trimester of pregnancy in women without
clinical indications (normal pregnancy) [C,
I].
Validation
This report was externally peer reviewed. The 1982 Canadian Federal Task
Force on High Risk Pregnancies and Prenatal Record Systems recommended
ultrasound examinations not be used in routine pregnancies without specific
indications. The 1984 U.S. National Institutes of Health Consensus Conference
did not support the routine use of ultrasound screening. The Society of
Obstetrics and Gynecology of Canada recommended routine use of a single
ultrasound examination in the second trimester of pregnancy.
Sponsors
The Canadian Task Force on Preventive Health Care
developed this guideline with funding from Health Canada.
Selected
References
Source Document
Link to Full Text of this
review
Link to Summary Table of Recommendations of this review
Link to Selected References list of this review
Literature Search Update: Aug 3,
1998
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