ORP: Structured Programs and Interventions (2014)

Citation:

Polley BA, Wing RR, Sims CJ. Randomized controlled trial to prevent excessive weight gain in pregnant women. Int J Obes. 2002; 26(11): 1,494-1,502.

 

PubMed ID: 12439652
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To determine whether a stepped-care, behavioral intervention will reduce excessive weight gain during pregnancy.

Inclusion Criteria:
  • BMI more than 19.8
  • Age more than 18 years
  • Less than 20 weeks gestation
  • Informed consent.
Exclusion Criteria:
  • Underweight (BMI less than 19.8)
  • Age less than 18 years
  • First prenatal visit was more than 12 weeks gestation
  • High-risk pregnancy (drug abuse, chronic health problems, previous complications during pregnancy or current multiple gestation).
Description of Study Protocol:

Recruitment

Women were recruited before 20 weeks gestation from an obstetric clinic for low-income women at a hospital in Pittsburgh, PA, United States.

Design

Randomized controlled trial.

Intervention
  • Subjects were randomized by race ((black vs. white) and BMI category (normal weight vs. overweight) to the intervention or control group. Normal weight was defined as BMI 19.8 to 26.0 and overweight more than 26.0.
  • The intervention group received education about weight gain, healthful eating, exercise and individual graphs of their weight gain. Those exceeding weight gain goals were given more intensive intervention in the form of additional individualized nutrition and behavioral counseling. A stepped-care approach was used, where the woman was given increasingly structured behavioral goals at each visit if  her weight continued to exceed the recommended levels.
  • The control group received the standard nutrition counseling by hospital staff. Subjects were followed through pregnancy to their first postpartum clinic visit.

Statistical Analysis

  • Logistic regression was used to examine the effect of treatment group and BMI category on weight gain category [above the Institute of Medicine (IOM) recommended level vs. below]. Weeks of gestation at delivery was used as a covariate.
  • Analysis of variance was used for secondary aims
  • When significant interactions with weight category were observed, post hoc analyses were conducted to analyze the effects of treatment separately in normal-weight and overweight women. Pre-pregnancy weight was covaried in these analyses.
  • Intent-to-treat approach, including all subjects available at the post-pregnancy or postpartum assessments.
Data Collection Summary:

Timing of Measurements

  • Demographic and weight history information was obtained at recruitment
  • Weight was measured at every clinic visit
  • Postpartum weight was obtained at the first clinic visit after delivery (8±7.1 weeks)
  • Self-report measures of dietary intake and exercise expenditure were obtained at recruitment, 30 weeks gestation and six weeks postpartum.

Dependent Variables

  • Primary: Proportion of women who exceeded the IOM recommendations for weight gain (25 lb to 35 lb for normal weight women and 15 lb to 25 lb for overweight women)
  • Secondary:
    • Total weight gain during pregnancy (based on self-reported pre-pregnancy weight and weight at the last clinic visit prior to delivery)
    • Weigh gain from recruitment to delivery
    • Postpartum weight loss and weight retention
    • Behavior changes during pregnancy (dietary intake measured by the Block Food Frequency Questionnaire and exercise expenditure measured by the Paffenbarger Exercise Questionnaire)
    • Pregnancy complications and fetal outcomes.

Independent Variables

The stepped-care behavioral intervention.

Control Variables

  • Age
  • Race
  • Marital status
  • Education
  • Employment
  • Childbearing history
  • Pre-pregnancy weight
  • Weeks of gestation.
Description of Actual Data Sample:

Initial N

N=120:

  • 61 in treatment group (32 normal weight, 29 overweight)
  • 59 in control group (33 normal weight, 26 overweight).

Attrition (final N)

110 (92%) followed to delivery:

  • 57 in treatment group (30 normal weight, 27 overweight)
  • 53 in control group (31 normal weight, 22 overweight)
  • 74 (62%) of the 110 subjects were followed postpartum

Age

Mean 25.5±4.8 years.

Ethnicity

  • 39% black
  • 61% white.

Other Relevant Demographics

No statistically significant differences between groups on these demographic characteristics:

  • Marital status
  • Education
  • Employment
  • Childbearing history.

Location

Pittsburgh, PA, United States.

Summary of Results:

Key Findings

  • The intervention significantly decreased the percentage of normal-weight women who exceeded the IOM recommendations (33% vs. 58%, P<0.05)
  • There was a non-significant (P=0.09) effect in the opposite direction among overweight women (59% of intervention and 32% of control gained more than recommended)
  • Postpartum weight retention was strongly related to weight gain during pregnancy (R=0.89).
 
  Normal Weight Overweight
 

Control

(N=31)

Intervention

(N=30)

Control

(N=22)

Intervention

(N=27)

Pre-pregnancy BMI (kg/m2) 22.5±2.0 22.8±1.9 34.1±7.2 31.4±6.0b
Pre-pregnancy weight (kg) 59±6.9 62.1±6.1* 91.8±19.6 83.6±16.7b,c

Total weight gain (kg)

16.4±4.8

15.4±7.1

10.1±6.2

13.6±7.2b

    (range, kg) (6.8-30.9) (2.7-32.7) (-0.9-26.4) (1.4-29.1)

IOM categories of total weight gain

Exceed IOM recommend, N (%) 18 (58.1%) 10 (33.3%)* 7 (31.8%) 16 (59.3%)c
   Within IOM recommend, N (%) 8 (25.8%) 11 (36.7%) 8 (36.4%) 6 (22.2%)
   Below IOM recommend, N (%) 5 (16.1%) 9 (30.0%) 7 (31.8%) 5 (18.5%)
   Postpartum weight lossa -9.0±2.4 -9.6±3.5* -9.6±2.7 -9.1±4.1
   Net weight retention, kga  6.2±4.5  4.4±5.4  0.3±7.0  3.6±5.6

aPostpartum weights available for 74 participants and all postpartum weights adjusted for weeks postpartum; bmain effect of BMI category, P<0.001; cinteraction between treatment group and BMI category, P<0.01.

*Indicates a significant treatment effect for post hoc analyses within each BMI category.

Other Findings

  • There was a trend for a significant treatment group-by-BMI category interaction in the proportion of women who were able to recover from excessive weight gain during pregnancy and go on to have a total weight gain within or below IOM recommendations, P=0.07
  • Weight gained before recruitment was strongly related to excessive weight gain, P<0.0001 but none of the other demographic variables predicted excessive weight gain
  • The intervention had no significant effects on the average weight gain from pre-pregnancy to delivery or on weight gain from recruitment to delivery
  • Weight gain from pre-pregnancy to delivery was related to pre-pregnancy weight (P<0.05), weeks of gestation at delivery (P<0.05) and the amount of weight gained before recruitment (P<0.001), but was unrelated to any of the baseline demographic variables
  • Collapsing across treatment groups (N=110), neither dietary intake nor exercise level was related to the amount of weight gained during pregnancy nor to whether the women exceeded the IOM guidelines
  • There was a significant race effect for postpartum weight loss (P=0.01), with black women losing less weight than white women but no effect of race on weight retention (postpartum weight less pre-pregnancy weight).
Author Conclusion:
  • The intervention was effective in reducing the frequency of excessive weight gain in normal-weight women
  • The differential outcome for normal-weight and overweight women may suggest that the intervention was more effective for preventing problems with weight gain than for treating these problems
  • The most effective approach may be to begin to educate women during pregnancy about healthy eating and exercise and attempt to limit the frequency and extent of excessive pregnancy weight gain, and then continue such interventions in the postpartum period for those who have retained excessive amounts of weight.
Funding Source:
Not-for-profit
Magee-Womens Health Foundation
Reviewer Comments:
  • Since overweight black women were most likely to refuse entry into the study, those women who participated may not have been representative of this population 
  • Several limitations:
    • Sample size: Power was limited further by the fact that only 110 (92%) of 120 women completed the study and only 74 (62%) were available for postpartum measurements
    • Lower-income clinic population
    • The study was designed to minimize risk, and this may have limited its effectiveness. No differences between conditions in eating or exercise behavior were noted, perhaps reflecting the limited changes that were obtained, the difficulty of accurately assessing these behaviors and the limitations of the instruments selected for assessing diet and activity. Data were not collected on other behaviors that could potentially affect pregnancy-associated weight changes, including changes in smoking habits, breastfeeding and general lifestyle changes accompanying pregnancy and motherhood.
    • Self-reported pre-pregnancy weight and for a few cases self-reported postpartum weight.

 

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? ???
  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? No
3. Were study groups comparable? No
  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? No
  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.) ???
  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? No
  6.6. Were extra or unplanned treatments described? Yes
  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? ???
  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? ???
  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? ???
  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? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
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