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.
Prevention of Low Birth Weight/Preterm Birth
Prepared by Orlando P. da Silva, MD, FRCPC Department of Pediatrics, Division
of Neonatology, The University of Western Ontario
These recommendations were finalized by the Task Force in April 1994
Contents
Objective
To make recommendations for prevention of low birth weight (LBW) or preterm
birth in high-risk or low-risk pregnant Canadian women.
Burden
of Suffering
LBW is associated with about 75% of early neonatal mortality in both Canada
and the U.S. A U.S. study found that 83% of deaths were associated
with delivery <37 weeks and 66% with delivery <29 weeks. About
6% of infants born in Canada are of LBW. The average cost per admission
in the U.S. has been estimated to be over US$7,500 per infant, not including
long-term care. In developed countries, cigarette smoking is the
most important established factor with a direct causal impact on the rate
of intrauterine growth retardation (defined as birth weight <2,500 g
and gestational age >37 weeks). Other important factors include poor
gestational nutrition, low pre-pregnancy weight, primiparity, female sex
and short stature. Smoking, prior preterm delivery, spontaneous abortion
and low pre-pregnancy weight seem to play an important role in determining
the rate of preterm births.
Options
Multicomponent programs can include education; advice on working, smoking,
stress, usual activities, sexual practices, nutrition, and bed rest; self
monitoring of uterine activity; antenatal care, external support systems,
and specific obstetrical practices (regular cervical examinations, cervical
sutures, bed rest in the hospital, progestgens, -mimetics, and calcium
antagonists).
Outcomes
Infant mortality, birth weight and morbidity, preterm labour and delivery,
and nutritional status.
Evidence
The Cochrane Collaboration Database on Pregnancy and Childbirth and MEDLINE
(1966 to January 1994) were searched using the terms low birth weight,
prematurity and prevention. Experts were also contacted. Study results
were synthesized in table or graphic format only.
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, 2 to 3 times per year from January 1993 1992 to April
1994. Consensus was reached on final recommendations.
Benefits,
Harms, and Costs
Multicomponent programs have shown mixed results in high-risk and low-risk
pregnancies although before and after studies have shown reductions in
preterm deliveries from 5% to 7% before the program to 2% to 6% after the
program. However, these studies have significant methodological limitations.
6 RCTs and 1 nonRCT showed conflicting results and positive results only
in subgroup or regression analyses that account for baseline differences.
RCTs and meta-analyses have not shown improvements in rates of pre-eclampsia
or neonatal outcomes for women with pregnancy-induced high blood pressure
who take low-dose aspirin.
Social support programs have been evaluated in 4 RCTs and 1 meta-analysis
of 8 studies. The evidence is consistent in showing that social support
alone is not effective in overriding the cumulative effects of social and
biologic disadvantage.
Nutritional supplementation has been evaluated in a series of programs
(Nutritional Supplementation Programs for Women, Infants, and Children).
The programs decreased low and very low birth delivery by 1% to 2% and
increased birth weight from 0 to 60 g, and had better outcomes and costs
(for every $1 spent on the program the savings in medical care were $2.91).
The wide range of benefit shown in different studies can be attributed
to differences in the populations studied, in the supplements used, and
in methodological quality of the study design, and the clinical significance
of this difference is unclear. A Canadian program and a meta-analysis
showed similar results for birth weight and preterm delivery.
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 inconclusive evidence that multicomponent education programs to
prevent preterm delivery of low birth weight infants are effective for
women with low-risk pregnancies [C, II-3]
or high-risk pregnancies [C,
I].
-
There is fair evidence that programs of social support alone for women
with high-risk pregnancies do not prevent preterm birth [D,
I].
-
For women who are at high risk for undernutrition, there is inconclusive
evidence regarding diet supplementation programs in the prenatal period
to prevent low birth weight babies [C, I,
II-2].
Validation
This report was externally peer reviewed.
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
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