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

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 ≥7.8mmol/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), HOMA-IR (-0.15, 95% CI -0.33 to 0.03), or oral glucose tolerance tests at 2 hours (-0.13mmol/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.