GDM: Physical Activity (2008)

Citation:
 
Study Design:
Class:
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Quality Rating:
Research Purpose:
To test the hypothesis that continuing vigorous, sustained exercise on a regular basis throughout pregnancy adversely affects morphometric and neurodevelopmental outcome in offspring at 5 years of age.
Inclusion Criteria:

1. Cases:

Women who throughout pregnancy exercised, either running, aerobics or cross-country skiing, or engaged in a combination of these activities at least 3 times/wk for greater than 30 minutes/session.

2.  Control:

Women who exercised regularly before pregnancy but voluntarily stopped all sustained exercise (except walking) during pregnancy.

3.  Normal pregnancy

4.  Spontaneous vaginal delivery at term (38 to 42 weeks), with no evidence of fetal distress

5.  Screened for GDM at 28 wk gestation with 50 gm glucose challenge

6.  Pregnant participants were matched for the following:

smoking status (none), socioeconomic status, education, marital stability, maternal and paternal morphometry, parity, maternal work outside the home, preconceptional fitness and exercise type, frequency and duration, breastfeeding offspring, type of child care, and maternal change in weight during the 6-yr interval.

7.  Offspring matched for the following:

sex, birth order, gestational age at delivery, normal growth and development (measured by child being between the 10th and 90th percentile for growth during the first year, achievement of developmental milestones on schedule), absence of serious illness, type of child care outside the home, new siblings.

No child in either group had any formal preschool academic experience outside the home.

Exclusion Criteria:

1. Chronic hypertension

2. Pregnancy-induced hypertension

Description of Study Protocol:

Recruitment:  Participants were drawn from a much larger northern Vermont study and individually matched with the offspring of physically active control subjects who had been followed and evaluated in an identical manner.

Design:  Prospective-case control study

Blinding Used (if applicable):  Examiners masked to maternal exercise status during pregnancy.

Intervention (if applicable):  Study protocol:

1. Women

     a.  VO2Max measured before conception

     b.  dietary intake assessed 5 times during pregnancy using random 24 hour dietary recalls

     c.  weights taken at 5-yr postpartum

     d.  Health and demographic data were obtained at the time of initial enrollment and updated            1 year post partum and at the time of 5 year evaluation

2.  All infants had morphometric assessments taken by a single trained examiner within 2-hr of birth and within 1 mo of the 5th birthday. 

3.  Neurodevelopment testing within 1 mo of the 5th birthday in two or three, 90 to 120 minute sessions:

Statistical Analysis:  Student unpaired t-test were used to look at between group differences for morphometric parameters and neurodevelopment scores.   Least square regression was used to measure an effect of exercise volume on outcome parameters.  A power analysis was performed.

 

Data Collection Summary:

Timing of Measurements: Children's measurements were obtained at birth and 5 yo of age.   Mothers' variables were obtained as follows:

     a.  VO2Max measured before conception

     b.  dietary intake assessed 5 times during pregnancy using random 24 hour dietary recalls

     c.  weights taken at 5-yr postpartum

     d.  Health and demographic data were obtained at the time of initial enrollment and updated            1 year post partum and at the time of 5 year evaluation

Dependent Variables:

Children: 

Morphometrics at birth and 5-yr of age -- Measurements were performed in duplicate and the average was recorded:

  1.     weight (nearest 10gm at birth, 50 gm at 5 yo)/birth weight percentile
  2.     length (nearest millimeter)
  3.     circumferences: head, chest, abdomen (CV <3%)
  4.     skinfolds: triceps, subscapular (neasured to the nearest .1 mm)
  5.     ponderal index - wt(100)/ht3 - Index of axial vs soft tissue growth

Psychometric tests at 5-yr of age:

  1.     Wechsler Preschho and Primary Scale of Intelligence-Revised
  2.     Peabody Picture Vocabulary Test combined with the Expressive One Word Picture    Vocabulary Test
  3.     Clinical Evaluation of Language Fundamental
  4.     Early Reading Aibilty
  5.     Early Mathematics Ability
  6.     Bruininks-Oseretsky Test of Motor Proficiency
  7.     Developmental Test of Visual Motor Integration

Mothers:

  • VO2Max
  • Dietary intake
  • Weights
  • Health and demographic data

Independent Variables: 

  • Activity Level

Control Variables:  No control variables.  Matched controls used.

Description of Actual Data Sample:

Initial N:  40 women, 20 Exercisers and 20 controls; 12 girls and 8 boys in each group of offspring.

Attrition (Final N):  40, 20 Exercisers and 20 controls; 12 girls and 8 boys in each group of offspring.

Age:  31 + 1 year of age

Ethnicity: White

Other relevant demographics:  All had educational levels ranging from completeing junior college through postdoctoral training.  Family incomes were all in the upper quartile for the VT and county of residence and all women worked part or full time.

Anthropometrics: See table in summary of results

Location:  Vermont

 

 

 

Summary of Results:

Mothers

Maternal and paternal physical characteristics

 Physical Characteristics  Exercise Control P

Maternal Age

31 + 1  31+ 1 NS

Weight (kg)

 57.5 + 1.2  57.6 + 1.4 NS

Height (cm)

169.2 + 2.6  168.8 + 2.3 NS

Body Fat (%) 

 16.6 + 1.3 17.1 + 1.4 NS

VO2max

54.4 + 2.6 53.1 + 2.9 NS
Pregnancy weight gain (kg) 12.8 + 1.1 16.2 + 1.4 .01
5 yr weight change (kg) .1 + 1.5 .9 + 1.1 NS
Paternal weight (kg) 73.2 + 2.3 70.9 + 3.1 NS
Height (cm) 178.3 + 3.1 176.4 + 3.3 NS

Exercise group:  11 were runners, 9 did aerobics, 6 women also participated in cross-country skiing in the winter

Runners:  Before pregnancy runners ran 21 to 68 km/wk at a pace between 4.3 and 5.5 min/km at an intensity of 58%-83% of O2Max.

Aerobics:  Participated 4-10 sessions/wk at intensities between 62% and 88% of O2Max. 

Those who continued exercise during pregnancy maintained performance level >60% of the above levels.  In the first 1/2 of pregnancy it averaged 73% (range, 65 - 109%), and in the second 1/2 74% (range, 62% to 122%)

Offspring

The parameters in the offspring of the exercising women were significantly lighter and leaner.  These differences were maintained at 5-yrs of age.

 Morphometry of offspring at birth:

 

 Offspring Characteristics Exercise Control P

Weight (gm)

3400+80  3640+70  0.01
Height (cm) 51.7 + .3 51.9 + .3 NS
Ponderal Index 2.46 + .06 2.63 + .06 NS

 % Body fat

10.5 + 0.9   15.1 + 0.6  0.01

Fat mass, (gm)

360 + 30 550 + 30  0.01
Lean body mass(gm) 3040 + 50 3090 + 40 NS
Head Circumference (cm) 35.2 + .2 35.4 + .3 NS
Chest Circumference (cm) 34.1 + .2 34.5 + .3 NS

Abdominal Circumference (cm)  

30.9 + 0.2  33.6 + 0.3 0.01 

HC/AC, ratio

1.13 + 0.03  1.05 + 0.03 0.05
 

Morphometry of offspring at 5 years:

 Offspring Characteristics Exercise Control P

Weight (kg)

18.0 + .5  19.5 + .6 0.01
Height (cm) 109.0 + 1.1 110.2 + .9 NS
Ponderal Index 1.40 + .02 1.47 + .03 .05

Sum of 5 skinfolds (mm)

37 + 1 44 + 2 0.01

Arm fat area (cm2)

7.89 + .35  9.23 + .36 0.01
Arm muscle area (cm2) 15.09 + .28 14.79 + .44 NS
Arm circumference (mm) 17.0 + .2 17.4 + .2 NS
Head Circumference (mm) 51.8 + .3 51.4 + 1.0 NS
Chest Circumference (mm) 55.2 + .5 54.3 + 1.1 NS

Abdominal Circumference (cm)  

50.9 + .6 51.9 + 1.2 NS

HC/AC, ratio

 1.02 + .01  .99 + .01 NS

 

Neurodevelopmental characteristics at 5 years of age:

 

Developmental Test Complex

Exercise

Control

p

General Intgelligence

125 + 2 117 + 3  0.01

Oral Language Skills  

119 + 2 109 + 3 0.01
Academic Readiness 100 + 2 98 + 2 NS
Motor Performance 123 + 2 124 + 3 NS
Perceptual-motor 108 + 2 111 + 3 NS

Overall Score  

115 + 1  111 + 2  0.05

Other Findings:  None reported.

Author Conclusion:

These data refute the hypothesis that continuing regular, vigorous, sustained exercise throughout pregnancy adversely affects morphometric and neurodevelopmental outcomes in offspring at 5 yrs of age.  While there was no deficit in any neurologic area examined for either group, offspring of mothers who exercised, scored higher on levels of general intelligence and oral language skills.  The offspring of exercising mothers were also leaner tending to plot near the 50th percentile vs children in the control group who weighed more (still on the curve) and had higher fat masses.  

The authors at this time can only speculate as to why these outcomes occurred.  With respect to morphometric measures, both groups breastfed and had similar diets, but the authors consider the possibility of maternal 24 hour average blood glucose levels which were not measured.  Regarding neurodevelopmental changes no cause can be identified, but the author considers fundamental differences in maternal-child interactions, different caregiver relationships or some stimulus associated with exercise, such as vibration.

 

Funding Source:
Government: NICHD
University/Hospital: MetroHealth Medical Center
Not-for-profit
0
Foundation associated with industry:
Reviewer Comments:

This was a well-designed and thorough study. The results are sufficient to support continued exercise during pregnancy with no adverse outcomes for either the mother or the child.  Individual woman should discuss exercise with their physician during pregnancy.

These findings also found that mothers who regularly engaged in vigorous activity throughout pregnancy gained less, but appropriate levels of weight.

These results are also provoactive in that they suggest a possible link between maternal exercise during pregnancy and reduced risk for childhood obesity in offspring.  This area will require further research.

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? Yes
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.) Yes
  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? N/A
  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? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  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.) Yes
  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? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  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)? N/A
  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? 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