Prenatal Strength Training May Lower Gestational Diabetes Risk

Key Takeaways

• In the primary intention-to-treat analysis, gestational diabetes occurred in 2% of the strength training group versus 7.3% of the control group, but the difference did not reach statistical significance.
• In an exploratory per-protocol analysis, gestational diabetes occurred in 0% of adherent intervention participants versus 7.3% of controls, and macrosomia occurred in 0% versus 6.3%, respectively; neither difference was statistically significant.
• The strength training group had significant quality-of-life improvement along with lower frequency and impact of pregnancy symptoms.
• Adverse events, including preterm birth, did not differ between the strength training and control groups.

Gestational diabetes prevention remains a persistent challenge in pregnancies complicated by excess weight, and evidence on exercise as a preventive strategy remains limited. Strength training has drawn less attention than aerobic activity in this setting, leaving open whether a structured program started in gestational weeks 12–14 and continued into late pregnancy could affect metabolic risk and maternal well-being. Investigators tested that question in a randomized trial.

In the randomized clinical trial, researchers enrolled 209 pregnant women with overweight or obesity. The structured strength training program ran from gestational weeks 12–14 to week 36 or delivery and was compared with a control group. The primary efficacy analysis followed the intention-to-treat principle, with an additional exploratory per-protocol analysis among intervention participants who met the predefined adherence criterion of at least 2 exercise sessions per week.

In the intention-to-treat analysis, gestational diabetes occurred in 2% of the intervention group and 7.3% of the control group, for a risk difference of −5.3 percentage points (95% CI, −12.5 to 0.5; P = 0.07), which did not reach statistical significance. No significant difference in macrosomia was observed in this analysis. Among adherent intervention participants in the exploratory per-protocol analysis, gestational diabetes occurred in 0% versus 7.3% of controls (risk difference, −7.3 percentage points; 95% CI, −14.3 to 3.0; P = 0.09), and macrosomia occurred in 0% versus 6.3% (risk difference, −6.3 percentage points; 95% CI, −13.1 to 4.5; P = 0.1). The strength training group also showed significant improvement in quality of life and reported lower frequency and impact of pregnancy symptoms. Adverse events, including preterm birth, were not observed to differ between groups.

Because the primary efficacy findings did not reach statistical significance and the stronger numerical differences were observed in an exploratory per-protocol analysis, the report does not support broader practice-change language. Only 48% of intervention participants with available adherence data met the predefined adherence target, and the authors cautioned that adherence was not randomized, so the per-protocol findings may be affected by confounding. Generalizability is limited to pregnant women with overweight or obesity.

The investigators interpreted the trial as showing significant improvement in maternal quality of life and reduced pregnancy-related symptom burden with structured prenatal strength training. Although the trial did not demonstrate a statistically significant reduction in gestational diabetes, trends toward lower gestational diabetes and related outcomes were observed, particularly among adherent participants. They called for larger trials to confirm the potential metabolic and obstetric benefits.

Clinician Questions

Do the gestational diabetes results from prenatal strength training reflect all randomized participants or only women who adhered to the program?

Both analyses were reported. In the primary intention-to-treat analysis, gestational diabetes occurred in 2% of the intervention group and 7.3% of controls, but the difference was not statistically significant (P = 0.07). In the exploratory per-protocol analysis, gestational diabetes occurred in 0% of adherent intervention participants versus 7.3% of controls (P = 0.09). Of 75 intervention participants with adherence data, 36 (48%) met the predefined adherence criterion of at least 2 exercise sessions per week.

Which pregnancies does the prenatal strength training trial most directly apply to?

The findings most directly apply to pregnant women with overweight or obesity, because that is the population named in the trial title and described in the report. The available information does not establish the same level of applicability for pregnancies more broadly.

How was gestational diabetes assessed in the prenatal strength training trial?

Gestational diabetes screening was performed between 24 and 28 weeks of gestation using a 50-g O'Sullivan test, with a 1-hour blood glucose level above 140 mg/dL considered abnormal. Participants with an abnormal screening result underwent a 100-g oral glucose tolerance test, with gestational diabetes diagnosed when at least 2 specified glucose thresholds were abnormal.