A 12-week exercise program performed during the second trimester does not prevent gestational diabetes in healthy pregnant women

Blikk på forskning utarbeides i samarbeid med Journal of Physiotherapy, som trykker forskningspresentasjonene under betegnelsen Critically Appraised Papers, CAPs.

Synopsis

Summary of: Stafne SN et al (2012) Regular exercise during pregnancy to prevent gestational diabetes.Obstet Gynecol119: 29–36. [Prepared by Nora Shields, CAP Editor.] 

Question: Does a 12-week exercise program prevent gestational diabetes and improve insulin resistance in healthy pregnant women with normal body mass index (BMI)?

Design: Randomised, controlled trial with concealed allocation and blinded outcome assessment.

Setting: Two University hospitals in Norway.

Participants: White adult women with a single fetus. High-risk pregnancies or diseases that would interfere with participation were exclusion criteria. Randomisation of 855 participants allocated 429 to the exercise group and 426 to a control group.

Interventions: Both groups received written advice on pelvic floor muscle exercises, diet, and lumbo-pelvic pain. In addition, the intervention group participated in a standardised group exercise program led by a physiotherapist, once a week for 12 weeks, between 20 and 36 weeks gestation. The program included 30–35 minutes low impact aerobics, 20–25 minutes of strength exercises using body weight as resistance and 5–10 minutes of stretching, breathing, and relaxation exercises. They were also encouraged to follow a 45-minute home exercise program at least twice a week. The control group received standard antenatal care and the customary information given by their midwife or general practitioner.

Outcome measures: The primary outcomes were the prevalence of gestational diabetes, insulin resistance estimated by the homeostasis model assessment method (HOMA-IR), and fasting insulin and oral glucose tolerance tests at baseline and at the end of the training period. Fasting and 2-hour glucose levels were measured in serum by the routine methods. Gestational diabetes was diagnosed as fasting glucose level 2-hour value ≥ 7.8 mmol/L. Secondary outcome measures were weight, BMI, and pregnancy complications and outcomes.

Results: 702 participants completed the study. At the end of the 12-week program, there was no difference in the prevalence of gestational diabetes (25 (7%) of intervention group compared with 18 (6%) of control group), HOMAIR (–0.15, 95% CI –0.33 to 0.03), or oral glucose tolerance tests at 2 hours (–0.13 mmol/L, 95% CI –0.28 to 0.03) between the groups. Fasting insulin was significantly lower in the intervention group by 1.0 international units/mL (95% CI –0.1 to –1.9). The groups did not differ significantly on any of the secondary outcomes. Adherence to the exercise protocol in the intervention group was 55%. A per protocol analysis of 217 women in the intervention group who adhered to the exercise program demonstrated similar results with no difference in prevalence of diabetes.

Conclusion: A 12-week exercise program undertaken during the second trimester of pregnancy did not reduce the prevalence of gestational diabetes in pregnant women with BMI in the normal range. 

Commentary

Diabetes causes 5% of deaths worldwide, mainly in lowto-middle income countries and affects over 220 million people. About 60% of women with gestational diabetes mellitus (GDM) are at high-risk of developing Type 2 diabetes within 20 years (Boerschmann et al 2010). Current guidelines (Artal and O’Toole 2003) recommend regular exercise for pregnant women, including those who are sedentary. However, the effect of exercise on the development of GDM has been studied little, and the results of published studies are conflicting (Callaway et al 2010). Stafne et al (2012) have presented a paper of excellent methodological quality, reported according to CONSORT, and dealing with the controversial question of exercise during pregnancy. In this trial, the incidence of GDM was similar in both groups and levels of insulin resistance (HOMA-IR) also showed no difference between groups, regardless of adjustment for factors such as baseline fasting insulin levels. Of note, only 55% of women in the exercise group adhered to the study protocol and 10% of women in the control group exercised at least three days per week. An exploratory analysis, in which adherent women in the exercise group were compared with women in the control group, showed no difference in incidence of GDM, but fasting insulin was lower in the adherent women. Given that the trial was not powered to compare adherent and non adherent women, results of the exploratory analysis should be interpreted with caution. The lack of adherence to the exercise protocol among the study participants confirms a pressing priority in this area is effective promotion of exercise in pregnant women. It is unclear whether the effect on GDM alone is large enough for pregnant women to feel it justifies the time, effort, and cost of an exercise program. Other trials should determine whether any specific type of exercise before pregnancy prevents GDM. Despite the uncertainty about whether exercise during pregnancy prevents GDM, exercise provides other benefits such as reducing depressive symptoms (Robledo-Colonia 2012) suggesting we should continue prescription of exercise during pregnancy. A potentially successful strategy to encourage pregnant women to exercise might be to introduce regular leisure-time physical activity as a routine part of obstetric care (Ramirez-Velez et al 2011). 

Robinson Ramírez-Vélez, Physical Exercise and Sports Research Group, Physiotherapy Program, Manuela Beltrán University, Bogotá, Colombia 

References

Artal R (2003)Br J Sports Med37: 6–12.

Boerschmann H (2010)Diabetes Care33: 1845–1849.

Callaway LK (2010)Diabetes Care33: 1457–1459.

Ramírez-Vélez R (2011)Trials28: 60.

Robledo-Colonia AF (2012)J Physiother58: 9–15.