An Evidence Review for the U.S. Preventive Services Task Force
October 2008
Prepared by Mei Chung, MPH; Gowri Raman, MD; Thomas Trikalinos, MD, PhD; Joseph Lau, MD; and Stanley Ip, MD.
Corresponding Author: Mei Chung, MPH, Center for Clinical Evidence Synthesis, Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, 800 Washington Street, Box 63, Boston, MA 02111; E-mail, mchung1@tuftsmedicalcenter.org.
This study was conducted by the Tufts-New England Medical Center Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality, Rockville, Maryland (contract no. 290-02-0022).
The information in this report is intended to help clinicians, employers, policymakers, and others make informed decisions about the provision of health care services. This report is intended as a reference and not as a substitute for clinical judgment.
This report may be used, in whole or in part, as the basis for the development of clinical practice guidelines and other quality enhancement tools, or as a basis for reimbursement and coverage policies. AHRQ or U.S. Department of Health and Human Services endorsement of such derivative products may not be stated or implied.
This report was first published in Annals of Internal Medicine in September 2008 (Ann Intern Med 2008;149:565-82; http://www.annals.org).
Contents
Abstract
Introduction
Methods
Results
Discussion
References
Abstract
Background: Evidence suggests that breastfeeding decreases the
risk for many diseases in mothers and infants. It is therefore important
to evaluate the effectiveness of breastfeeding interventions.
Purpose: To systematically review evidence for the effectiveness of
primary care–initiated interventions to promote breastfeeding with
respect to breastfeeding and child and maternal health outcomes.
Data Sources: Electronic searches of MEDLINE®, the Cochrane Central
Register of Controlled Trials, and CINAHL from September
2001 to February 2008 and references of selected articles, restricted
to English-language publications.
Study Selection: Randomized, controlled trials of primary care–initiated interventions to promote breastfeeding, mainly in developed
countries.
Data Extraction: Characteristics of interventions and comparators,
study setting, study design, population characteristics, the proportion
of infants continuing breastfeeding by different durations, and
infant or maternal health outcomes were recorded.
Data Synthesis: Thirty-eight randomized, controlled trials (36 in
developed countries) met eligibility criteria. In random-effects metaanalyses,
breastfeeding promotion interventions in developed countries
resulted in significantly increased rates of short- (1 to 3
months) and long-term (6 to 8 months) exclusive breastfeeding
(rate ratios, 1.28 [95% CI, 1.11 to 1.48] and 1.44 [CI, 1.13 to
1.84], respectively). In subgroup analyses, combining pre- and
postnatal breastfeeding interventions had a larger effect on increasing
breastfeeding durations than either pre- or postnatal interventions
alone. Furthermore, breastfeeding interventions with a component
of lay support (such as peer support or peer counseling)
were more effective than usual care in increasing the short-term
breastfeeding rate.
Limitations: Meta-analyses were limited by clinical and methodological
heterogeneity. Reliable estimates for the isolated effects of
each component of multicomponent interventions could not be
obtained.
Conclusion: Evidence suggests that breastfeeding interventions are
more effective than usual care in increasing short- and long-term
breastfeeding rates. Combined pre- and postnatal interventions and
inclusion of lay support in a multicomponent intervention may be
beneficial.
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Introduction
Human milk is the natural nutrition for all infants. According
to the American Academy of Pediatrics, it is
the preferred choice of feeding for all infants.1 The goals
of Healthy People 2010 for breastfeeding are an initiation
rate of 75% and continuation rate of 50% at 6 months and
25% at 12 months after delivery.2 A survey of U.S.
children in 2002 indicated that only 71% had ever been
breastfed, and the percentage of infants who continue to be
breastfed to some extent is 35% at 6 months and 16% at
12 months.3 Although the breastfeeding initiation rate is
close to the goal set by Healthy People 2010, according to
this survey, the breastfeeding continuation rates at 6 and
12 months fall short.
Evidence suggests that breastfeeding decreases risks for
many diseases in infants and mothers. In children, breastfeeding
has been associated with a reduction in the risk for
acute otitis media, nonspecific gastroenteritis, severe lower
respiratory tract infections, atopic dermatitis, childhood
leukemia, and the sudden infant death syndrome. In mothers,
a history of lactation has been associated with a reduced
risk for type 2 diabetes and breast and ovarian cancer.4 According to the American Academy of Pediatrics,
some of the obstacles to initiation and continuation of
breastfeeding include insufficient prenatal education about
breastfeeding, disruptive maternity care practices, and lack
of family and broad societal support.5 Effective interventions
reported to date include changes in maternity care
practices, such as those implemented in pursuit of the Baby-Friendly Hospital Initiative (BFHI) designation6,7 and
worksite lactation programs.8 Some of the other interventions
implemented include peer-to-peer support, maternal
education, and media marketing.9
Our review is based on an evidence report10 that
was requested by the Center on Primary Care, Prevention,
and Clinical Partnerships at the Agency for
Healthcare Research and Quality, on behalf of the U.S.
Preventive Services Task Force, to support the Task
Force's update of its 2003 recommendations on counseling
to promote breastfeeding.11 Together with the
Tufts Evidence-based Practice Center, these agencies
jointly developed an analytic framework for study questions
to evaluate the available evidence to promote and
support breastfeeding (Figure 1). Five linked key questions
were proposed in the analytic framework:
- What are the effects of breastfeeding interventions
on child and maternal health outcomes?
- What are the effects of breastfeeding interventions
on breastfeeding initiation, duration, and exclusivity?
- Are there harms from interventions to promote and
support breastfeeding?
- What are the benefits and harms of breastfeeding on
infant or child health outcomes?
- What are the benefits and harms of breastfeeding on
maternal health outcomes?
The contextual questions regarding the effectiveness
of health care system influences on interventions to promote
breastfeeding and the potential benefits and harms
related to such interventions can be answered by synthesizing
the available scientific evidence for each key question.
To avoid redundant work, a joint decision was
made to adopt results from our earlier Agency for
Healthcare Research and Quality evidence report4 to
address questions 4 and 5 on the benefits and harms of
breastfeeding for infants and mothers. Table 112-84
presents a synopsis of that report's findings on questions
4 and 5. We address only questions 1 to 3 in this article.
Specifically, we examine the effects of primary care–initiated interventions to support or promote breastfeeding
on child and maternal health outcomes and
breastfeeding rates, as reported in randomized, controlled
trials (RCTs) from developed countries. We also
document reported harms from interventions to promote
and support breastfeeding.
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Methods
Data Sources
This systematic review focuses on recent evidence
(September 2001 to February 2008) and updates a previous
systematic review
85 conducted for the U.S. Preventive
Services Task Force to support its 2003 recommendation
on counseling to promote breastfeeding (available at
http://www.ahrq.gov/clinic/uspstf/uspsbrfd.htm). We searched for
English-language articles in MEDLINE®, the Cochrane Central
Register of Controlled Trials, and CINAHL from September
2001 to February 2008 by using such Medical Subject
Heading terms and keywords as
breastfeeding, breast milk feeding,
breast milk, human milk, nursing, breastfed, infant nutrition,
lactating, and lactation. We also reviewed reference lists of
a related systematic review
86 for additional studies.
Study Selection
We included RCTs published from September 2001
to February 2008 that included any counseling or behavioral
intervention initiated from a clinician's practice (office
or hospital) to improve the breastfeeding initiation rate
or duration of breastfeeding among healthy mothers or
members of the mother–child support system (such as
partners, grandparents, or friends) and their healthy term
or near-term infants (≥35 weeks' gestation or ≥2500 g).
We focused our review on studies conducted in developed
countries; however, because of the widespread interest in
the BFHI, we also included RCTs of the BFHI that were
conducted in Brazil and Belarus.
We considered interventions conducted by various providers
(lactation consultants, nurses, peer counselors, midwives,
and physicians) in various settings (hospital, home,
clinic, or elsewhere) to be eligible as long as they originated
from a health care setting. We considered maternity services to
be primary care for this review. We also included such health
care system interventions as staff training. We excluded community- or peer-initiated interventions. Control comparisons
were any usual prenatal, peripartum, or postpartum care, as
defined in each study. Studies needed to report rates of breastfeeding
initiation, duration of breastfeeding, or exclusivity
of breastfeeding to be included. Figure 2 shows our
search and selection process.
Data Extraction and Quality Assessment
One investigator extracted data from each study, and
another confirmed them. The extracted data included
study setting, population, control, description of intervention
(type, person, frequency, and duration), definitions of
breastfeeding outcomes (initiation, exclusivity, and duration),
definitions of health outcomes in both mothers and
children (when provided), and analytic methods.
Classification of Breastfeeding Interventions
Breastfeeding interventions can include a combination
of individual components, such as structured breastfeeding
education or professional or lay support. We defined 3
categories of breastfeeding intervention: those that included
a component of formal or structured breastfeeding
education, those that included a component of either professional
or lay breastfeeding support, or those that did not
include the aforementioned components. The first 2 categories
are not mutually exclusive. Table 2 shows complete
details.
Definitions
We classified breastfeeding regimens as exclusive or
nonexclusive. Studies used different definitions of exclusive
breastfeeding ("no supplement of any kind," "including
water while breastfeeding," or "occasional formula is permissible
while breastfeeding"); we adopted all of those definitions.
We classified all other breastfeeding regimens
(full, partial, mixed, or nonspecified) as nonexclusive.
We defined breastfeeding initiation as any breastfeeding
at discharge or up to 2 weeks after delivery. We also
defined a priori breastfeeding durations of 1 to 3 months as
short-term, 4 to 5 months as intermediate-term, 6 to 8
months as long-term, and 9 or more months as prolonged.
We categorized studies with breastfeeding durations
shorter than 1 month as "no breastfeeding" in our metaanalyses.
Two investigators assessed the methodological quality
of all eligible studies by using criteria developed by the
U.S. Preventive Services Task Force.87 We assigned
each article a quality rating of "good," "fair," or "poor."
The criteria for quality assessment of primary studies included
randomization techniques, allocation concealment,
clear definitions of outcomes, intention-to-treat analysis,
and statistical methods. A third investigator reviewed studies
for which the first 2 investigators gave discordant quality
ratings. We reached final grades for those studies via
consensus. We performed subgroup analyses to examine
the effects of study quality on the meta-analysis results. We
also based our qualitative conclusions on good- or fair-quality
studies.
Data Synthesis and Analysis
We calculated the rates of breastfeeding initiation and
short-term, intermediate-term, long-term, and prolonged
breastfeeding for both the intervention and control groups
in each study. We recorded the exclusivity of breastfeeding
and did the same calculations for the exclusive breastfeeding
rates.
Meta-analysis and Meta-regression
We used the rate ratio (relative risk) as the metric of
choice to quantify the effectiveness of each breastfeeding
promotion intervention. We used the DerSimonian and
Laird model for random-effects meta-analysis88 to obtain
summary estimates across studies. We tested for heterogeneity
by using the Cochran Q test, which follows a
chi-square distribution to make inferences about the null
hypothesis of homogeneity (considered significant at P < 0.100) and quantified its extent with I2.89,90 The I2
statistic ranges between 0% and 100% and quantifies the
proportion of between-study variability that is attributed to
heterogeneity rather than chance.
We used random-effects meta-regression (fitted with
restricted maximum likelihood) to explore whether the effectiveness
of breastfeeding interventions depends on
breastfeeding duration, provided that at least 6 studies with
relevant information were available.91,92
Subgroup Analyses
We performed subgroup analyses according to various
study factors, such as study quality, timing of intervention
(prenatal, postpartum, or combined prenatal and postpartum),
and different components of breastfeeding interventions.
We used a Z test to compare summary estimates
between the subgroups.
We used Intercooled Stata, version 8.2 (Stata, College
Station, Texas) for all analyses. All P values are 2-tailed and
considered significant when less than 0.05 unless otherwise
indicated.
Role of the Funding Source
The Agency for Healthcare Research and Quality and
the U.S. Preventive Services Task Force helped formulate
the initial study questions but did not participate in the
literature search, determination of study eligibility criteria,
data analysis or interpretation, or preparation of the manuscript.
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Results
We identified 4877 abstracts in our search and evaluated
a total of 147 full-text articles. Thirty-eight RCTs met
our eligibility criteria: 32 parallel RCTs described in 33
publications,93–125 4 clustered RCTs,126-129 and
2 quasi-RCTs described in 3 publications130-132 (Figure 2). Table 3 shows the 36 trials that were conducted in
developed countries (Australia, Canada, Denmark, France,
Italy, Japan, Netherlands, New Zealand, Scotland, Sweden,
Singapore, United Kingdom, and United States).
Two trials on BFHI were conducted in developing countries
(Brazil and Belarus).
The interventions included system-level breastfeeding
support (such as BFHI and training of health professionals),
formal breastfeeding education, professional
support (such as from lactation consultants, midwives,
nurses, physicians, or other health professionals), lay
support (such as peer support or counseling), motivational
interviews, delayed or discouraged pacifier use,
and skin-to-skin contact. Several components were often combined into a single, multifaceted breastfeeding
intervention.
Eleven trials (29%) were of good quality, 14 trials
(37%) were of fair quality, and 13 trials (34%) were of
poor quality. The Appendix Table describes the criteria of quality assessment used
to reach the overall quality rating for each RCT. Table 3 summarizes the study characteristics.
Key Question 1
What are the effects of breastfeeding interventions on
child and maternal health outcomes?
The effects of breastfeeding interventions on child
health outcomes were reported in 3 RCTs published in 4
articles.93–95,126 One of these RCTs also reported
maternal health outcomes. One good-quality study,126
PROBIT (Promotion of Breastfeeding Intervention Trial),
was conducted in Belarus, and 2 fair-quality studies93–95 were conducted in low-income populations in the
United States. We could not combine the results from
these RCTs in a meta-analysis because the interventions
were dissimilar.
The PROBIT study was a good-quality, cluster, multicenter
RCT involving a total of 17 046 mother–infant
pairs from urban and rural areas in Belarus. Infants in the
intervention group (a modeled BFHI) had a significant
reduction in the risk for 1 or more gastrointestinal infections
(adjusted odds ratio, 0.60 [95% CI, 0.40 to 0.91])
and atopic dermatitis (adjusted odds ratio, 0.54 [CI, 0.31
to 0.95]) compared with those in the control group but
had no significant reduction in respiratory tract infections.126 The 2 fair-quality RCTs, involving a total of 564 mother–infant pairs in low-income families in the United
States, reported discordant results. The major drawbacks of
these 2 RCTs were high rates of loss to follow-up or missing
breastfeeding data. One study showed no significant differences
between the 2 groups (hospital and home visits by 2
study lactation consultants vs. usual care) in the risk for gastrointestinal
illnesses, respiratory tract diseases, or otitis media,94,95 whereas the other study found that the risk for 1 or
more diarrheal episodes during the study was decreased in the
intervention group (home visits by trained breastfeeding peer
counselors) compared with the control group (17.5% vs.
37.5%; P = 0.02).93 The latter study also reported that
mothers in the intervention group were less likely than those
in the control group to have menses return at 3 months
(47.6% vs. 66.7%; P = 0.03). Cessation of menstrual periods
for the first few postpartum months during exclusive breastfeeding
is a normal physiologic process.
Key Question 2
What are the effects of breastfeeding interventions on
breastfeeding initiation, duration, and exclusivity?
Effects on Breastfeeding Initiation and Duration
We found substantial heterogeneity across eligible trials
in the actual breastfeeding promotion interventions (including
many different combinations of "intervention
components") and their implementation, timing, and intensity
(Table 3). Furthermore, the definition of "usual" or
"routine" care varied substantially because of differences in
background social support and health care systems in the
various countries. The sociodemographic characteristics of
the study populations also varied.
As shown in Figure 3, breastfeeding promotion interventions
resulted in an increased rate of breastfeeding initiation
(rate ratio, 1.04 [CI, 1.00 to 1.08]) and short-term
breastfeeding (rate ratio, 1.10 [CI, 1.02 to 1.19]) compared
with usual care, with significant statistical heterogeneity
in both cases. It is questionable whether these trivial
effects have any real-world effect. For short-term exclusive
breastfeeding, the relative risk was 1.72 (CI, 1.00 to 2.97),
again with evidence of statistical heterogeneity (Figure 4).
When we excluded the 2 RCTs from developing countries,98,126 the results for any breastfeeding initiation and
short-term breastfeeding were no longer significant. However,
intervention effects on short- and long-term exclusive breastfeeding
were significant (rate ratios, 1.28 [CI, 1.11 to 1.48]
and 1.44 [CI, 1.13 to 1.84], respectively), with evidence for
statistically significant heterogeneity for short-term exclusive
breastfeeding (I2. 55%; P = 0.006).
Table 4 describes subgroup analyses performed according
to the timing of breastfeeding promoting interventions
(prenatal, postnatal, and combinations thereof).
Overall, the direction of the effects favors breastfeeding
promotion interventions over usual care and was statistically
significant for some subgroups (Table 4). We found
no clear pattern for the outcome of any breastfeeding with
respect to intervention timing. However, for short-term
exclusive breastfeeding, the summary point estimates of the
corresponding rate ratios are larger for the combination of
pre- and postnatal interventions (P = 0.01, Z test).
We performed subgroup analyses on the effects of different
components of breastfeeding interventions on
breastfeeding initiation, duration, and exclusivity compared
with usual care. Again, multiple components were
often combined into a single, multifaceted breastfeeding
intervention. Our analyses compared only a specific component
within a multifaceted intervention with usual care.
Indirect comparison of the pooled effect sizes between different
intervention components could be misleading,
because other components in the intervention and control
groups may not be the same across the different
subgroups. Overall, we did not find that formal or structured
breastfeeding education or individual-level professional
support significantly affected the breastfeeding
outcomes. We did find that lay support significantly
increased the rate of any and exclusive breastfeeding in
the short term by 22% (CI, 8% to 48%) and 65% (CI,
3% to 263%), respectively. Meta-regression suggested
that larger effects (compared with usual care) were associated with longer duration for any breastfeeding (P = 0.04) (Table 5).
Finally, the summary rate ratios of breastfeeding initiation
and duration did not statistically significantly differ
across RCTs of different quality grades (data not shown).
Differences in Absolute Breastfeeding Durations
Ten RCTs in 11 publications100,102,105,107,110,112,119,121,125,130,131 reported the differences
in the absolute breastfeeding duration between
breastfeeding intervention and usual care groups. The
follow-up durations ranged from 2 weeks to 1 year. We
did not perform meta-analyses because the intervention
components and units of analysis for the breastfeeding
outcomes varied greatly across these trials. Seven of the
10 RCTs did not show a significant difference in absolute
breastfeeding duration between the intervention
and control groups. The other 3 RCTs, 2 of good quality and 1 of fair quality, showed that delayed pacifier use
(>4 weeks) was more effective than early pacifier use
(within 2 to 5 days)102 and system-level professional
support105 and postpartum skin-to-skin care107 were more effective than usual care in increasing breastfeeding duration.
Interventions Involving Family Members
We identified 2 poor-quality RCTs involving family
members in breastfeeding intervention. These 2 RCTs
were graded poor quality because of incomplete reporting
of trial protocol (for example, randomization and blinding)
and nonrigorous definitions of breastfeeding outcomes.
One study compared the effects of breastfeeding classes for
expectant fathers to control group classes of baby care
and safety on rates of any breastfeeding initiation and
any breastfeeding at 2 months.113 This study found
that more women whose partners attended the breastfeeding
classes initiated breastfeeding than did women
whose partners attended the control class (74% vs. 41%;
P = 0.02). However, the rate of any breastfeeding at 2
months did not significantly differ between the intervention
and control groups. The other study examined
the role of a grandmother (maternal mother) or a close
female confidante (sister or friend) of the mother's own
choice in supporting breastfeeding.122 This study found no significant difference in breastfeeding initiation
or duration between the breastfeeding promotion
with a female confidante and the routine prenatal care
without a female confidante.
Key Question 3
Are there harms from interventions to promote and support
breastfeeding?
We did not identify any study specifically designed to
examine harms from interventions to promote and support
breastfeeding (regardless of design). None of the eligible
RCTs reported harms from the breastfeeding interventions.
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