Health Disparities

HD: Effectiveness of Nutrition Intervention Methods (2010)


Bonuck KA, Trombley M, Freeman K, McKee D. Randomized, controlled trial of a prenatal and postnatal lactation consultant intervention on duration and intensity of breastfeeding up to 12 months. Pediatrics. 2005 Dec; 116 (6): 1,413-1,426.

PubMed ID: 16322166
Study Design:
Randomized controlled trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To determine whether an individualized, prenatal and post-natal lactation consultant intervention resulted in increased cumulative intensity of breastfeeding up to 52 weeks.

Inclusion Criteria:
  • English- or Spanish-speaking
  • Twin or singleton pregnancy (originally, but during data analysis, only mothers of singletons were included)
  • Intent to keep the infant
  • Plans to remain in the center and its affiliated hospital system for prenatal and infant care up to 12 months
  • At least two contact telephone numbers
  • Gestation before 24 weeks.
Exclusion Criteria:
  • HIV-positive status
  • Chronic therapy with medications incompatible with breastfeeding
  • Pre-gestational diabetes mellitus
  • Human T-cell leukemia virus-1
  • Breast reduction surgery
  • Hepatitis B or C.
Description of Study Protocol:


Recruited from two hospital-affiliated health centers:

  • From one center, participants were recruited by a research assistant from the center's mandatory prenatal class
  • From the other center, social work staff members recruited participants.


  • Eligible participants randomly assigned to:
    • Intervention group that received lactation consultant intervention
    • Control group that received standard care.
  • Data collection included:
    • One prenatal baseline interview
    • Eight telephone interviews at one, two, three, four, six, eight, 10 and 12 months after birth.

Blinding Used

Research assistant and lactation consultants were not blinded to treatment group, but data were not shared between research assistants and lactation consultants.


Intervention included:

  • Two attempted individual meetings with a lactation consultant, prenatally and post-partum in the hospital or at home  
  • Telephone consultation up to 12 months
  • Breastfeeding education and counseling
  • Assistance garnering support from families, schools, workplaces and health care provider
  • Nursing bra
  • Manual or mini-electric breast pumps, depending on circumstance.

Statistical Analysis

  • Unadjusted differences between groups tested for significance with T-tests, chi-square tests and the Mantel-Haenszel test
  • Differences between sites on 60 baseline variables were analyzed
  • Bivariate associations between breastfeeding intensity scores and other variables analyzed with Wilcoxon rank sum tests and Spearman rank correlations
  • Logistic regression models analyzed breastfeeding intensity scores as outcome variables with significant covariates, treatment group, interaction between treatment group and country of origin as independent factors
  • Analyses used a intention-to-treat model.
Data Collection Summary:

Timing of Measurements

Data collection included:

  • One prenatal baseline interview
  • Eight telephone interviews at one, two, three, four, eight, 10 and 12 months after birth.

Dependent Variables

  • Breastfeeding intensity through Week 13 (total, 13)
  • Breastfeeding intensity through Week 52 (total, 52)
    • Weekly scores based on Index of Breastfeeding Status that measures the percentage of breast milk an infant receives, compared with the total amount of feedings. A score of one is exclusive breast milk, whereas a score of seven is exclusive formula.
    • Intensity scores derived by summing intensity scores obtained each week
    • Dichotomous variable created (low vs. high breastfeeding) by using the median as a cut-point.

Independent Variables

  •  Demographics
    • Age
    • High school graduate
    • Marital status
    • Birthplace (foreign born)
    • Race or ethnicity
    • Medicaid recipient
    • Parity
    • Prior experience breastfeeding
    • Intentions to breastfeed.
  • Birth and postpartum experiences
    • Birth location (study hospital)
    • Delivery time (day or night)
    • Who baby left hospital with (mother)
    • Birth type (vaginal or Cesarean)
    • Birth weight (low birth weight or normal weight)
    • Neonatal Intensive Care Unit (NICU) (yes or no)
    • Roomed in (yes or no)
    • First breastfeeding attempt (zero to four hours; after four hours)
    • Advised on breastfeeding by prenatal care provider (yes or no)
    • Asked if wanted to nurse in delivery room by hospital staff (yes or no)
    • When first considered how to feed infant (before pregnancy, first trimester or later).
  • Treatment group
    • Intervention
    • Control.
Description of Actual Data Sample:

Initial N

382 women were randomly assigned:

  • 188 in Intervention Group
  • 194 in Control Group.

Attrition (Final N)

304 women with at least one post-natal follow-up data point.

  • 145 in Intervention Group
  • 159 in Control Group.


Mean age in years ± standard deviation (SD)

  • Intervention Group: 25.48±6.39
  • Control Group: 24.99±6.09.

Ethnicity (N)

  • Black
    • 52 (35.9%) in Intervention Group
    • 58 (36.5%) in Control Group.
  • Hispanic
    • 82 (56.6%) in Intervention Group
    • 90 (56.6%) in Control Group.

Other Relevant Demographics

  • No statistically significant difference between groups in age, race or ethnicity, high school education, marital status, foreign birth, Medicaid coverage, parity, previous breastfeeding experience or intentions with regard to breastfeeding
  • No statistically significant difference between groups in birth and postpartum experience variables, including infant birth weight (low birth weight vs. normal weight).


Bronx, New York.

Summary of Results:

Key Findings

  • Any breastfeeding: The Intervention Group was significantly more likely to breastfeed at each week up to and including Week 20 (53.0% vs. 39.3%, P<0.028) with the exception of Week 18
  • Breastfeeding of 50% or more: Significantly more women in the Intervention Group gave 50% or more breast milk up to and including Week Nine (45.8% vs. 33.1%, P<0.030)
  • Exclusive breastfeeding:  Exclusive breastfeeding rates were not significantly different between intervention and control groups at any of the 52 weeks observed.

Logistic Regression: Risk of Low Breastfeeding (Compared to High Breastfeeding) (N=304)



Week 13
Odds Ratio [95% Confidence Interval (CI)]

Week 52
Odds Ratio [95% Confidence Interval (CI)]

Intent at Baseline

3.04* (1.22 to 7.58)

3.02* (1.21 to 7.56)

10.51* (2.97 to 37.15)
10.05* (3.04 to 33.20)
1.57 (0.85 to 2.87)
2.22* (1.19 to 4.15)
Breast milk (referent)
Logarithm of Age Years
0.92* (0.88-0.96)
Age Less than 24 years N/A
3.15* (1.83 to 5.42)
24 years or more (referent) N/A
Race or Ethnicity Black
0.44* (0.24 to 0.79)
0.37* (0.20 to 0.67)
1.75 (0.60 to 5.13)
1.40 (0.48 to 4.10)
Hispanic (referent)
Medicaid No
1.05 (0.61 to 1.82)
0.71 (0.41 to 1.23)
Yes (referent)
Treatment Group/ Country of Origin Control/US-born
5.22* (2.43 to 11.22)
5.25* (2.44 to 11.29)
0.90 (0.40 to 2.04)
1.06 (0.47 to 2.40)
1.67 (0.78 to 3.53)
1.15 (0.54 to 2.45)
Intervention/foreign-born (referent)
Model R2

* P<0.05
N/A: Data not given in paper's table.

  • In bivariate analysis, variables with associations yielding P-values of less than 0.20 were used in initial multivariate models
  • Women who were undecided about feeding intentions and those intending to formula feed exclusively at baseline had a significantly greater risk of low breastfeeding at both 13 and 52 weeks. At 52 weeks only, women who planned to both breast and formula feed combined had a significantly greater risk of low breastfeeding. 
  • Younger women were at greater risk of low breastfeeding at both 13 and 52 weeks
  • Black women were at a significantly lower risk of low breastfeeding compared to the Hispanic referent group at both 13 and 52 weeks
  • Women who were in the Control Group and born in the U.S. had a significantly greater risk of low breastfeeding at both 13 and 52 weeks, compared to foreign-born women in the intervention group
  • Logistic regression models also analyzed a sub-sample of the participants who had at least one other child at baseline. These models yielded similar results, except being undecided about feeding intentions no longer a significant risk factor for low breastfeeding at both 13 and 52 weeks and planning to combine breast and formula feeding was no longer a significant risk factor at 52 weeks. Women who had not breastfed previously had a significantly greater risk of low breastfeeding at 52 weeks but not at 13 weeks, compared to women who had previously breastfed.
  • Alternative logistic regression models used the same set of covariates, except that treatment group was used in place of the treatment group or country of origin interaction terms. ORs and 95% CIs for covariates in the alternative logistic regression model were essentially unchanged from those shown above.
Author Conclusion:
  • At three and 12 months, control subjects receiving standard care in urban primary care health centers had 90% and 150% increased risk of low breastfeeding, respectively, compared with the Intervention Group. We observed similar rates of exclusive breastfeeding between the two groups, which suggests that the intervention was not effective in helping women to breastfeed exclusively. Our most striking finding was the strength with which country of origin modified the effect of treatment group. US-born women were five to eight times as likely to have low breastfeeding intensity, depending on observation period and parity, compared with the foreign-born Control, foreign-born Intervention and US-born Intervention Groups. Therefore, our intervention was highly effective in raising the breastfeeding level of US-born women to that of foreign-born women, whose scores did not differ according to treatment group. 
  • In contrast to the aforementioned results, race and ethnicity did not modify the effect of treatment group significantly. That is, the intervention was no more effective among one racial or ethnic group than another. Furthermore, in sharp contrast to recent national studies, black women were 50% to 60% more likely to have a high intensity of breastfeeding, compared with a reference group of women who identified themselves as Hispanic. Presumably, this finding is related to demographic distributions in the study's locale, i.e., New York City. New York City experienced a 41% increase in the West Indian population between 1990 and 2000, nearly all of whom identify themselves as black. West Indians represented 25% of the black population in New York City in 2000. Compared with the United States, West Indian nations have considerably higher rates of any and exclusive breastfeeding and longer duration of breastfeeding.
  • This "best-practices" intervention was effective in increasing breastfeeding duration and intensity. Breastfeeding promotion should focus on US-born women and exclusive breastfeeding.
Funding Source:
Government: United States Department of Agriculture, the Maternal and Child Health Bureau, and the Agency for Healthcare Quality and Research
Reviewer Comments:
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? ???
  6.6. Were extra or unplanned treatments described? ???
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes