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ORP: Nutrition Prescription for Gestational Weight Gain (2014)

Citation:
Thornton YS, Smarkola C, Kopacz SM, Ishoof SB. Perinatal outcomes in nutritionally monitored obese pregnant women: A randomized clinical trial.
J Natl Med Assoc. 2009 Jun; 101(6): 569-577.
 
PubMed ID: 19585925
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
  • To compare perinatal outcomes of obese pregnant women treated in the conventional manner (control croup) to outcomes of nutritionally monitored obese pregnant women (study group)
  • To determine the effects of weight stabilization during pregnancy in obese pregnant women between the control and study groups on perinatal morbidity and on birth weight of their newborns
  • To determine perinatal differences in the study group's adherence vs. non-adherence to a prescribed nutritional regimen applicable to the general practice of obstetrics
  • To evaluate perinatal outcomes of obese pregnant women who had a gain of 15 pounds or more during their pregnancy compared to those who gained fewer than 15 pounds, irrespective of whether they were in the control or study group
  • To evaluate perinatal outcomes of obese pregnant women who had a gain of fewer than 10 pounds during their pregnancy compared to those who gained 10 pounds or more, irrespective of whether they were in the control or study group.
Inclusion Criteria:
  • Pregnant with a single fetus between 12 and 28 weeks of gestation
    • Gestational age based on patient's last normal menstrual period with clinical examination and confirmed with a mid-trimester sonographic study
    • If the patient was uncertain of her last normal menstrual period, an earlier sonogram was performed.
  • BMI of 30kg/m or more.
Exclusion Criteria:

Pre-existing diabetes, hypertension or chronic renal disease.

Description of Study Protocol:

Recruitment

  • Potential volunteers were approached at their prenatal care visits for possible participation
  • After the study was explained, their BMI was calculated based on the women's pre-pregnancy weight as reported by the patient and height as measured at the visit
  • Obese (BMI 30kg/m2 or more) women were then invited to participate in the study before they knew to which group they would be assigned.

Design

Randomized, parallel-group trial.

Blinding Used

  • No blinding for study personnel mentioned
  • Patients in the study (monitored) group were requested not to weigh themselves at home to ensure that it would not influence diet intake.

Intervention

  • Control group (unmonitored) was told to "eat to appetite" following general prenatal dietary guidelines
  • Both groups: 
    • Were counseled at least once by a registered dietitian regarding conventional prenatal nutrition guidelines
    • Were asked to wear similar clothing at each visit and were weighed at each visit
      • Weight was measured at time of entry to the study, before delivery and at six weeks postpartum
      • The newborn was weighed by the delivery room nurse immediately after delivery.
    • Were encouraged to walk 30 minutes per day
    • Has assessments of blood pressure and urine for glucose, protein and ketones
    • If the ability to assess uterine fundal height was compromised due to a large abdominal panniculus, serial sonographic examinations were requested monthly in order to assess fetal growth
    • Neonatal outcome was measured with Apgar scoring
    • Medical records were reviewed after the patient delivered to assess:
      • Antepartum and intrapartum complications
        • Development of gestational diabetes
        • Ketonuria
        • Pre-eclampsia
        • Shoulder dystocia.
      • Type of delivery
      • Macrosomia
      • Anesthesia
      • Intra-operative and post-operative complications
        • Wound dehiscence/infection
        • Post-partum hemorrhage.
  • Study group (monitored): 
    • Followed guidelines similar to patients with the diagnosis of gestational diabetes
    • Based on weight at study entry, placed on an 18kcal to 24kcal per kg balanced nutritional regimen:
      • 40% carbohydrates
      • 30% protein
      • 30% fat.
    • No patient received a diet of fewer than 2,000 calories
    • Asked to record in a diary all of the foods and beverages consumed during each day 
    • Records were reviewed at each prenatal visit by the physician
    • Six weeks after delivery, the patient was weighed during her post-partum visit and exited the study
    • Food diary notebooks were collected from each patient at the end of the study
      • Adherence was defined as recording daily food intake and bringing the logbook to the clinic visit for review by the physician
      • Non-adherence was defined as not recording food intake for more than a week and failing to bring the logbook to clinic for review.

Statistical Analysis

  • Performed using SPSS (SPSS Inc, Chicago, Illinois)
  • Two T-tests were performed to show there was no significant difference in baseline pregnancy weight, T(230) = 1.49, P=0.060 and BMI T(230) = 1.90, P=0.134, between control group and study groups
  • For objectives one, three, four and five:
    • Multi-variate analysis of variance (MANOVA) was used to compare the five continuous peri-natal outcomes variables:
      • Maternal last weight before delivery
      • Maternal six-week post-partum weight
      • Mean weight difference between the baseline pregnancy weight and weight before delivery
      • Gestational age at birth
      • Infant birth weight.
    • X2 was used to compare the 11 categorical peri-natal variables:
      • Gestational diabetes (0 = no, 1 = yes)
      • Preeclampsia
      • Ketonuria
      • Gestational hypertension
      • Pre-term delivery
      • Post-term delivery
      • Labor induction
      • Macrosomic infant
      • Apgar score
      • Cesarean delivery
      • Hemorrhage or infection post-partum (0= no infection, 1 = infection, 2 = hemorrhage).
  • For objective two:
    •  X2 test was used to compare the two categorical perinatal variables:
      • Macrosomic infant
      • Apgar score.
    • T-test was performed for infant birth weight.
  • Levene's equality of error variance used to test the homogeneity of variance assumption.

The analyses included 116 patients in each group and were performed according to the intent-to-treat principle.

Data Collection Summary:

Timing of Measurements

 Between June 1998 and May 2005:

  • Morristown Memorial Hospital: 1998  to 2000
  • St. Luke's-Roosevelt Hospital Center: 2001 to 2002
  • Jamaica Hospital Medical Center: 2002 to 2005.

Dependent Variables

    • Taken or measured at clinic visits (patients were asked to wear similar clothing at visits): 
      • Maternal last weight before delivery
      • Maternal six-week postpartum weight
      • Gestational age at birth.
    • Infant birth weight: Weighed by the delivery room nurse immediately after delivery
    • Medical records were reviewed after the patient delivered to assess: 
      • Gestational diabetes
      • Preeclampsia
      • Ketonuria
      • Gestational hypertension
      • Pre-term delivery
      • Post-term delivery
      • Labor induction
      • Macrosomic infant
      • Apgar score
      • Cesarean delivery
      • Hemorrhage or infection post-partum.

Independent Variables

 Dietary guidelines:

  • Control group (unmonitored): Told to "eat to appetite" following general pre-natal dietary guidelines
  • Study group (monitored):
    • Followed guidelines similar to patients with the diagnosis of gestational diabetes
    • Based on weight at study entry, placed on an 18kcal to 24kcal per kg balanced nutritional regimen
    • 40% carbohydrates, 30% protein and 30% fat
    • No patient received a diet of fewer than 2,000 calories.

Control Variables

All were counseled at least once by a registered dietitian regarding conventional pre-natal nutrition guidelines.

 

Description of Actual Data Sample:

Initial N

257 patients were enrolled and randomized.

Attrition (Final N)

232 completed study (116 in each group):

  • Eight lost to follow-up in the intervention group
  • 17 lost to follow-up in the control group.

Age

  Control Group Study Group
  (N=116) (N=116)
Median age, years 27.3 26.8

 

Ethnicity

  Control Group Study Group
Race/Ethnicity (N=116) (N=116)

African American

49 (42.2%) 46 (39.7%)

Caucasian

27 (23.3%) 25 (21.6%)

Latina

25 (21.6%) 29 (25%)

Indian

15 (12.9%) 16 (13.7%)

 

Other Relevant Demographics

  Control Group Study Group
  (N=116) (N=116)
Parity    

Nulliparous

20 (17.2%) 19 (16.3%)

Parous

96 (82.8%) 97 (83.7%)
Marital status    

Single

31 (26.7%) 28 (24.1%)

Married/de facto

85 (73.3%) 88 (75.9%)

Anthropometrics

  Control Group Study Group P value
  (N=116) (N=116)  
Baseline pregnancy weight, lbs. 214.20 (SD 50.71) 204.11 (SD 51.80) 0.060
Body mass index, kg/m2 38.22 (SD 7.48) 37.41 (SD 7.01) 0.134

Location

Ambulatory obstetric clinics of three tertiary care medical centers. Each one is an urban, public clinic of a teaching hospital:

  • Morristown Memorial Hospital
  • St. Luke's-Roosevelt Hospital Center
  • Jamaica Hospital Medical Center. 
Summary of Results:
  • Objective 1: Peri-natal outcome differences between control and study groups:
    • There were statistically significant differences  (Wilks' λ=27.54, P<0.001, effect size = 0.327) between the study and control groups for:
      • Maternal last weight before delivery
      • Maternal six-week post-partum weight
      • Mean weight difference between the baseline pregnancy weight and weight before delivery
      • Gestational age at birth
      • Infant birth weight.
    • There were statistically significant differences in the groups:
      • Maternal last weight before delivery: F(1,232) = 21.22, P<0.001
      • Maternal six-week post-partum weight: F(1,232) = 17.42, P<0.001
      • Differences from maternal baseline weight to their last weight before delivery: F(1,232) = 89.76, P<0.001.
    • Women in the control group (9%) were more likely to experience gestational hypertension than women in the study group (3%), X2 (1,N=232) = 3.99; P=0.046
    • Ketonuria was not observed in any study participants.
  • Objective 2: Effects of weight stabilization on peri-natal morbidity and on birth weight of newborns: 
    • No significant differences found between the control group and the study groups on their newborns regarding:
      • Macrosomia
      • Apgar score
      • Infant birth weight.
  • Objective 3: Differences in peri-natal outcomes regarding adherence vs. non-adherence with prescribed nutritional regimen in the study group:
    • 90 of the 116 study group participants adhered to the nutritional program
    • There was a statistically significant difference:
      •  For peri-natal outcomes between the adherent and non-adherent groups (Wilks' λ = 53.038, P<0.001, effect size = 0.707)
      • Between the groups for:
        • Maternal last weight before delivery: F(1,114) = 4.13, P<0.05
        • Maternal six-week post-partum weight: F(1,114) = 5.65, P<0.05
        • Weight difference between the baseline pregnancy weight and weight before delivery: F(1,114) = 4.13, P<0.001
        • Infant birth weight: F(1,114) = 24.97, P<0.001
    • Women in the study group who did not adhere to the nutritional regimen compared to those women in the study group who did adhere were:
      • More likely to have gestational diabetes and preeclampsia
      • Induced labor
      • Cesarean delivery
      • Give birth to macrosomic infants
      • Retain more weight during and after pregnancy.

 

  Adherence   Non-adherence    
  (N=90) 95% CI (N=26) 95% CI P-Value³
Infant birth weight, g¹ 3,388(418.10) 3,272 to 3,503 4,004 (879.89) 3,789 to 4,219 <0.001
Last weight before delivery, lbs¹ 211 (46.34) 201 to 221 232 (48.32) 214 to 250 <0.05
Six-week post-partum maternal weight, lbs¹ 194 (46.84) 184 to 204 219 (50.33) 201 to 238 <0.05
Mean gain difference from baseline weight to last weight before delivery¹ 5 (10.64) 3.5 to 7.9 31 (10.74) 26.7 to 35.0 <0.001
Gestational diabetes² 2 (2.2)   9 (34.6)   <0.01
Preeclampsia² 2 (2.2)   5 (19.2)   <0.01
Labor induction² 12 (13.3)   10 (38.5)   <0.01
Cesarean delivery² 9 (10)   16 (61.5)   <0.01
Macrosomic infant² 2 (2.2)   7 (27)   <0.001

1Mean (standard deviation); continuous data.

2 N (percentage); categorical data.

3 P-values between groups tested with ANOVA for continuous variables and X2 for the categorical variables.

  • Objective 4: Participants who gained 15 pounds or more during pregnancy:
    • Statistically significant differences were found between the two groups (those who gained less than 15 pounds and those gaining 15 pounds or more, irrespective of group assignment) for four continuous peri-natal variables (Wilks' λ=56.28, P<0.001, effect size = 0.555) and for four categorical variables (using X2)
    • Those who gained 15 pounds or more:
      • Were typically in the control group 
      • Typically gave birth to heavier babies
      • Did not lose as much weight six weeks post-partum
      • Were more likely to have:
        • Gestational diabetes
        • Preeclampsia
        • Undergo cesarean delivery
        • Have labor induced

 

  Weight Gain Less Than 15lbs   Weight Gain 15 lbs or More    
  (N=92) 95% CI (N=140) 95% CI P Value³
Last weight before delivery, lbs¹ 218 (54.75) 208 to 229 238 (46.85) 229 to 246 <0.01
Six-week post-partum maternal weight, lbs¹ 201 (55) 190 to 211 221 (47) 212 to 230 <0.01
Mean gain difference from baseline weight to last weight before delivery¹ 4.44 (9.32) 1.8 to 7.0 32 (14.24) 30 to 34 <0.001
Infant birth weight, g¹ 3,411 (468) 3,292 to 3,528 3,651 (634) 3,555 to 3,746 <0.01
Gestational diabetes² 4 (4)   26 (19)   <0.01
Preeclampsia² 2 (2)   16 (11)   <0.01
Labor induction² 12 (13)   41 (29)   <0.05
Cesarean delivery² 13 (14)   45 (32)   <0.01
Group type²         <0.001

Study group

78 (67.2)   38(32.8)    

Control group

14 (12.1)   102 (87.9)    

1Mean (standard deviation); continuous data.

2 N (percentage); categorical data.

3 P-values between groups tested with ANOVA for continuous variables and X2 for the categorical variables.

  • Objective 5: Participants who gained fewer than 10 pounds during pregnancy:
    • Statistically significant differences were found between the two groups (those who gained less than 10 pounds and those gaining 10 pounds or more, irrespective of group assignment) for four continuous per-natall variables (Wilks' λ = 37.49, P<0.001, effect size = 0.453).
  • There were statistically significant differences in the groups for:
    • Maternal last weight before delivery
    • Maternal six-week postpartum weight
    • Mean weight difference between the baseline pregnancy weight
    • Weight before delivery.
Author Conclusion:
  • Obese pregnant women may be placed on a healthy, well-balanced, monitored nutritional program during their antepartum course without adverse peri-natal outcomes
  • Those monitored patients who were adherent by following the prescribed nutritional program and maintaining a daily food diary demonstrated less peri-natal morbidity compared to their non-adherent or unmonitored counterparts.
Funding Source:
Other: not mentioned
Reviewer Comments:
  • Study limitations mentioned in discussion:
    • The study group (monitored patients) self-reported their nutritional regimen, which can be less reliable than objective measurements
    • Conclusions regarding the development of gestational diabetes, preeclampsia and fetal macrosomia in the adherent vs. non-adherent group of patients should be made with caution due to low sample numbers in these categories.
  • Reviewer comments/questions:
    • Nothing was mentioned as to how they determined that the patients were actually consuming the prescribed 40% carbohydrate, 30% protein and 30% fat, no less than 2,000 calorie diet. Although physicians reviewed the diaries for completion, were the diaries entered into an analysis program?
    • If an RD was available to counsel the patients, why wasn't a RD (who might have more extensive training on nutrition content of food) reviewing the diaries
    • No blinding was mentioned. Were the study personnel who reviewed the diaries blinded to the participant's weight?
    • How detailed were the diaries? Did anyone sit down and clarify the entries with the participants (for example, writing down "1 bowl of cereal and milk" would have very different nutrients depending on what kind of cereal and milk. Is it "two cups of Lucky Charms and one cup whole milk" or "one-half cup Bud Brans and one-half cup skim milk?")
    • Were any measures taken to ensure that the patients wrote down their intake on a daily basis instead of recalling food intake at the end of the week? (I deal with food diaries on a daily basis and this is extremely common. No matter how detailed we are with instructions on recording it daily, we have patients who will try to fill out an entire week's diary while sitting in our waiting room to be considered in "adherence.")
    • Did breastfeeding have an effect on six-week post-partum weight loss?
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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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? Yes
  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? No
  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? ???
  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? N/A
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? ???
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? ???