Prevention of gestational diabetes: feasibility issues for an exercise intervention in obese pregnant women. Regular exercise during pregnancy to prevent gestational diabetes: a randomized controlled trial. Effects of a partially home-based exercise program for women with gestational diabetes. Exercise in gestational diabetes. An optional therapeutic approach?
To examine the feasibility of an individualized exercise program to prevent gestational diabetes mellitus (GDM) in obese pregnant women.
                The study was a pilot randomized controlled trial with obese pregnant women (intervention group, individualized exercise program [n = 25]; control group, usual care [n = 25]). Average weekly energy expenditure (MET hours per week and kilocalories per week) of exercise-specific activity was assessed during pregnancy using the Pregnancy Physical Activity Questionnaire. Fasting glucose and insulin and homeostasis model assessment of insulin resistance (HOMA-IR) were assessed at baseline and 20, 28, and 36 weeks' gestation.
                Of the women in the intervention group, 16 of 22 (73%) achieved more than 900 kcal/week of exercise-based activity at 28 weeks compared with 8 of 19 women in the control group (42%), P = 0.047. However, insulin resistance (HOMA-IR) did not differ between the groups.
                This intervention was feasible and prompted a modest increase in physical activity. However, we are not confident that this intervention would be sufficient to prevent GDM. To assess whether exercise during pregnancy can prevent gestational diabetes and improve insulin resistance.
                A total of 855 women in gestational week 18-22 were randomly assigned to receiving a 12-week standard exercise program (intervention group) or standard antenatal care (control group). The exercise program followed standard recommendations and included moderate-intensity to high-intensity activity 3 or more days per week. Primary outcomes were gestational diabetes and insulin resistance estimated by the homeostasis model assessment method. For the power calculation, we assumed a gestational diabetes prevalence of 9% in the control group and a prevalence of 4% in the exercise group (risk difference of 5%). Under these assumptions, a two-sample comparison with a 5% level of significance and power of 0.80 gave a study population of 381 patients in each group.
                At 32-36 weeks of gestation there were no differences between groups in prevalence of gestational diabetes: 25 of 375 (7%) in the intervention group compared with 18 of 327 (6%) in the control group (P=.52). There were no differences in insulin resistance between groups when adjusting for baseline values. Only 55% of women in the intervention group managed to follow the recommended exercise protocol. No serious adverse events related to physical exercise were seen, and the outcomes of pregnancy were similar in the two groups.
                There was no evidence that offering women a 12-week standard exercise program during the second half of pregnancy prevents gestational diabetes or improves insulin resistance in healthy pregnant women with normal body mass indexes.
                : ClinicalTrials.gov, www.clinicaltrials.gov, NCT00476567. To examine the effectiveness of a partially home-based, moderate-intensity aerobic exercise program for women with gestational diabetes.
                This was a randomized experimental design. Thirty-three women with gestational diabetes were randomly assigned to the exercise or the no-exercise group. Subjects underwent hemoglobin A1C assay and submaximal cycle ergometer fitness tests at baseline and at study conclusion. Subjects kept diaries of home fasting and 2-hour postprandial blood glucose determinations. Exercise subjects were asked to exercise for 30 minutes three to four times weekly at 70% of estimated maximal heart rate for the weeks of study participation. Two exercise sessions weekly were supervised by the investigator, and two were unsupervised at home. Control-group subjects were asked to maintain their current activity level.
                Daily fasting and postprandial blood glucose levels, hemoglobin A1C, incidence of exogenous insulin therapy, and incidence of newborn hypoglycemia were not different between the groups. There was a training effect in the exercise group (P = .005) but not in the control group (P = .25). A significant decline in daily grams of carbohydrate consumed was observed in the control group (P = .03), but not in the exercise group (P = .97). No complications were found in the subjects who exercised.
                A partially home-based exercise program did not reduce blood glucose levels, but did result in a modest increase in cardiorespiratory fitness. The intervention appeared safe. Forty-one patients with gestational diabetes requiring insulin were enrolled in a randomized study to investigate the efficacy of an exercise program in normalizing glucose tolerance. Seventeen of 21 patients completed the exercise program while maintaining normoglycemia and obviating insulin therapy. Maternal and neonatal complications did not differ between the study and control groups. The type of program described appears to be safe and can serve as a model for exercise prescription for pregnant diabetic women to attain improved glucose tolerance.
There is insufficient evidence to recommend, or advise against, diabetic pregnant women to enrol in exercise programs. Further trials, with larger sample size, involving women with gestational diabetes, and possibly type 1 and 2 diabetes, are needed to evaluate this intervention.
[Note: The six citations in the awaiting classification section of the review may alter the conclusions of the review once assessed.]