The Effects of Aerobic Water Exercise on Pregnancy
Condition: Pregnancy Related; Physical Activity
Study type: Interventional

Summary: 
      Objective: To assess the relationship between maternal cardiovascular capacity and aerobic
      water exercise during the gestational periods of hemodynamic overload. Study design:
      randomized clinical trial, with 41 healthy pregnant women assigned to one of two groups:
      Control and Water exercise. Maternal cardiovascular capacity (maximum oxygen consumption,
      cardiac output, stroke volume, heart rate and mean arterial pressure), physical performance
      (relative HR, treadmill speed and self-perceived exertion) and neonatal outcome (gestational
      age, weight, Apgar index and length of infant's hospitalization) were assessed. Means were
      evaluated by dependent and independent t-tests, and proportions by the chi-square method
      (p<0.05). Results: The control variables showed that the groups were homogeneous. Water
      exercise was associated with maintenance of VO2max, increase in stroke volume and cardiac
      output, and better performance on stress tests in the third trimester of gestation. No
      significant difference in neonatal variables was observed. Conclusion: Water exercise
      maintained cardiovascular capacity and performance under submaximal stress, and did not
      affect hemodynamic adaptation to gestation or neonatal outcome.
    

Detailed description: 
      INTRODUCTION

      Significant hemodynamic changes take place during the short period of pregnancy, very often
      placing a major burden on the maternal cardiovascular system. Normal pregnancy is
      characterized by an increase in cardiac output (CO), stroke volume (SV), heart rate (HR) and
      blood volume, and decrease in arterial pressure and vascular resistance. Classic studies have
      demonstrated an increase of up to 50% in maternal CO during the second and third trimesters.
      These circulatory adaptations are responsible for supplying nutrients and oxygen to the
      placenta and the fetus.

      The physiological changes that follow regular exercise improve training efficiency and
      performance, defining the concept of adaptation to exercise or aerobic training. Exercise
      causes the heart and lungs to be more efficient by increasing cardiovascular capacity or
      resistance. CO, SV and maximum oxygen consumption (VO2max) increase while HR and AP decrease.
      The importance of these effects on overall health has been recognized by the most outstanding
      medical and scientific groups. Therefore, regular exercise has been widely promoted and a
      large number of women decide to begin or continue to exercise during pregnancy.

      This change in women's behavior has become a matter of concern among obstetricians and has
      important practical implications - is the maternal body apt to bear the hemodynamic burden of
      pregnancy in association with exercise stress? Studies on the effects of exercise on
      pregnancy are scarce and show conflicting results, probably due to differences in exercise
      frequency, intensity, type, duration, and gestational age at training initiation.

      Aiming at standardizing exercise practice and thus promote materno-fetal health, the American
      College of Obstetricians and Gynecologists (ACOG) issued, in 1985, guidelines for exercise
      during pregnancy. In subsequent reviews, new recommendations were added, and water exercise
      during pregnancy was recommended.

      Water exercise offers some particular benefits that include the maintenance of body
      temperature, control of gestational edema, and increase in diuresis. Moreover, it can be
      easily performed up to the end of pregnancy, which favors compliance. These advantages added
      to the fact that it has no adverse effect on the fetus explain the preference for this kind
      of exercise during pregnancy.

      Considering the lack of scientific evidence of the effects of exercise during pregnancy, and
      the results obtained in our previous work, the purpose of this study was to assess the
      relationship of aerobic water exercise during the gestational periods of greater hemodynamic
      burden with maternal cardiovascular capacity and neonatal outcomes.

      METHODS

      This study is part of a project approved by the Committee of Research Ethics of the Botucatu
      Medical School-UNESP on May 10, 1999.

      Study design: randomized clinical, without intention to treat. Study subjects: All the
      eligible women who volunteered to participate were sequentially enrolled and randomized to
      one of two groups according to a computer-generated randomization list of numbers created
      with Epi-Info software. Each sequential number corresponded to a sealed opaque envelope
      containing the information on the randomization group in order to ensure concealment. Group 1
      consisted of 29 women engaged in Water Exercise, and group 2 included 31 pregnant women not
      participating in the program (control). Variables: the independent variable studied was the
      practice of water exercise. The control variables, which were assessed at baseline, included
      age, parity, pre-gestational body mass index (BMI), HR and MAP, smoking, sedentarism, and
      gestational age at baseline and at stress testing. The dependent variables regarding
      cardiovascular capacity and physical performance at the submaximal stress test were VO2max;
      SV; CO; HR and MAP, relative HR treadmill speed and scores obtained with the scale of Borg.
      Neonatal variables included gestational age, weight; Apgar index at minute 1 and at minute 5,
      and length (days) of infant's hospitalization.

      Assessment of cardiovascular capacity: performed during prenatal visits at 16-20, 28-33 and
      34-39 weeks. Cardiovascular capacity was evaluated by using a treadmill submaximal stress
      test, according to the protocol of Balke-Ware & Bruce that requires five minutes on treadmill
      at fixed incline and constant individualized speed with AP and HR monitoring. Assessment of
      physical performance at stress testing - for this purpose, relative HR, treadmill speed and
      the Borg scale scores, obtained during testing, were used. A specific questionnaire was
      administered to all subjects in order to quantify stress perception during testing.

      Data processing and analyses - given that the aim of this study was to assess the efficacy
      (exploratory and not intention-to-treat) of water exercise during pregnancy, our analysis
      included only the subjects who underwent cardiovascular assessment at the three study moments
      and missed no more than 2 exercise sessions/month. These data were stored in a specific
      database Statistical analysis was performed with SPSS software version 10.0.7. Means were
      compared using ANOVA followed by t-tests for independent (between groups) and dependent
      (within groups) samples. Data were adequately transformed when necessary. Proportions were
      compared by the chi-square test (X2). Statistical significance was set at 5% (p<0.005).
    

Intervention name(s): Water aerobic exercise
Intervention type(s): Other
Intervention description(s): The hydrotherapy program of Prevedel et al.14 was used. One-hour sessions, led by a physiotherapist under the supervision of an obstetrician, were held three times a week in an indoor swimming-pool heated at 28oC-32oC, and consisted of exercises of moderate intensity (60-70% of maximum heart rate). Subgroups of up to 10 subjects participated in each session. Sessions were offered at different times of the day (morning, afternoon, and evening).
The exercises included 5 phases: stretching, warm up, endurance training, strength training and relaxation with breathing exercises, in accordance with the recommendations of ACOG11.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Supportive Care
Keywords: Cardiovascular capacity; Water exercise; Hydrokinetic Therapy; Pregnancy; Perinatal outcomes