A randomized comparative trial of the efficacy and safety of exercise during pregnancy: Design and methods
Introduction
Exercise studies can be grouped into two categories: single bout of exercise tests in laboratory settings (whether a test is repeated or not), and exercise intervention studies in communities. The first asks people to exercise at a certain intensity and duration in order to measure detailed physiological changes and sometimes psychological changes. The latter observes adherence to an exercise regimen and uses relatively rough measures of the intensity and duration of exercise. The goal of such studies often is to observe exercise-related behavior modification. When the goal of a study is to observe the effects of exercise on pregnancy outcomes at home, this approach needs to be modified because gestational length may influence exercise effects. More detailed monitoring of the safety of exercise is also needed in pregnancy. Thus exercise interventions for high-risk pregnancies require special considerations. Currently the author and her research team are conducting a randomized comparative trial examining the effect of regular exercise among pregnant women at risk for preeclampsia.
A disorder of human pregnancy in which the normal hemodynamic response to pregnancy is compromised, preeclampsia is a leading cause of maternal morbidity (2–10% of all pregnancies) and mortality and is associated with a significant increase in perinatal mortality [1], [2], [3], [4]. A woman who experienced preeclampsia in a previous pregnancy is 1.6 times more likely to develop preeclampsia again than a woman without such history [5]. Preeclampsia is diagnosed primarily by the onset of hypertension and proteinuria in the latter half of gestation. Other manifestations of preeclampsia include generalized vasoconstriction, increased vasoactivity, reduced perfusion to organs, and platelet activation [6], [7]. Both the etiology and pathophysiology of preeclampsia are poorly understood. Currently, there are no conclusive preventive treatments available.
The purposes are to determine whether moderate intensity exercise during pregnancy reduces the incidence of preeclampsia and to assess the process (involving oxidative stress and the antioxidant process) hypothesized to explain the relationship between the effect of exercise and pathophysiologic progress of preeclampsia.
Section snippets
Aims
The following specific aims guided the trial design:
- 1.
To determine whether regular exercise during pregnancy reduces the incidence of preeclampsia.
- 2.
To determine whether regular exercise enhances the antioxidant process and reduces susceptibility to oxidative stress among pregnant women.
- 3.
To assess the associations among antioxidant activity, lipid peroxidation, and susceptibility to oxidative stress.
- 4.
To determine whether anioxidant activity and susceptibility to oxidative stress at various points in
Methods and design
This randomized trial compares moderate intensity exercise, repeated regularly during pregnancy, to a traditionally recommended maternal stretching exercise in women who have developed preeclampsia in a previous pregnancy and thus at high risk. Fig. 1 shows the overall design. Subjects are recruited before 14 weeks gestation, followed by a run-in period of 4 weeks. Those who succeed in scheduled weekly visits in the run-in phase are randomized to walking or stretching exercise. Both groups
Preliminary results
As of March 2006, 322 pregnant women had been referred by nurses at prenatal clinics or by themselves (Fig. 2). Of the 322 potential subjects, 217 (67%) were excluded for one reason or another, 11 are pending, 94 (29%) never communicated other than at the clinics, and 94 (29%) were randomized. Of the 217 women excluded, 191 (88%) did not get as far as consent. Seventy-two percent of them refused to participate and the rest appeared ineligible. Twenty-six women consented but left before being
Discussion
Use of regular exercise, walking in this case, as a preventive intervention for high-risk pregnant women is a new idea and it therefore required careful assessment of effectiveness and safety in our design. The design embodies a 4-week run-in period prior to randomization, a stretching exercise as the comparator, and the use of subjective and objective measures of daily physical activities throughout pregnancy. Additionally, interventions are tailored to individual supports based on
References (23)
- et al.
Risk factors for preeclampsia in healthy nulliparous women: a prospective multicenter study. The National Institute of Child Health and Human Development Network of Maternal–Fetal Medicine Units
Am J Obstet Gynecol
(Feb 1995) - et al.
Risk factors associated with preeclampsia in healthy nulliparous women. The Calcium for Preeclampsia Prevention (CPEP) study group
Am J Obstet Gynecol
(Nov 1997) - et al.
Leisure-time physical activity as an estimate of physical fitness: a validation study
J Clin Epidemiol
(1991) - et al.
A questionnaire for the assessment of leisure time physical activities
J Chronic Dis
(1978) - et al.
Test–retest reliability of the Minnesota Leisure Time Physical Activity Questionnaire
J Chronic Dis
(1986) Statistical considerations in the intent-to-treat principle
Control Clin Trials
(Jun 2000)- et al.
Beginning regular exercise in early pregnancy: effect on fetoplacental growth
Am J Obstet Gynecol
(Dec 2000) - et al.
Comparison of risk factors for preeclampsia and gestational hypertension in a population-based cohort study
Am J Epidemiol
(Jun 1 1998) - et al.
Epidemiology of eclampsia
Eur J Epidemiol
(Aug 1995) - et al.
Risk factors for preeclampsia, abruptio placentae, and adverse neonatal outcomes among women with chronic hypertension. National Institute of Child Health and Human Development Network of Maternal–Fetal Medicine Units
N Engl J Med
(Sep 3 1998)
Low-dose aspirin to prevent preeclampsia in women at high risk. National Institute of Child Health and Human Development Network of Maternal–Fetal Medicine Units
N Engl J Med
Cited by (17)
Associations between maternal physical activity and fitness during pregnancy and infant birthweight
2018, Preventive Medicine ReportsCitation Excerpt :All participants wore Polar S810 heart rate monitors and wristwatch devices to validate their adherence to the walking or stretching programs. Further details on the intervention and comparative groups can be found elsewhere (Yeo, 2006). For the purposes of this study, the data were collapsed across both groups and group allocation was controlled for in the analyses.
Diagnosis, evaluation, and management of the hypertensive disorders of pregnancy
2014, Pregnancy HypertensionCitation Excerpt :Among sedentary women with prior preeclampsia specifically, walking vs. stretching exercise did not alter pregnancy outcomes [276]. There is one ongoing RCT of moderate intensity exercise in women with prior preeclampsia [277]. RCT evidence is lacking for workload or stress reduction to prevent preeclampsia.
Longitudinal Changes of Depressive Symptoms in Sedentary Women Who Exercised During Pregnancy
2023, Women's Health ReportsThe effect of exercise during pregnancy on gestational diabetes mellitus in normal-weight women: A systematic review and meta-analysis
2018, BMC Pregnancy and ChildbirthPosture and gait biomechanical aspects during pregnancy and the importance of therapeutic exercise: Literature review
2015, Current Women's Health Reviews