Lifestyle approaches for preventing gestational diabetes mellitus (GDM) have produced mixed results.

The aim of the present study was to compare the effectiveness of 3 lifestyle interventions [healthy eating (HE), physical activity (PA), and both HE and PA (HE+PA)] with usual care (UC) in reducing GDM risk.

The present study was a multicenter randomized controlled trial conducted from 2012 to 2014 [the DALI (vitamin D and lifestyle intervention for GDM prevention) lifestyle study].

The study occurred at antenatal clinics across 11 centers in 9 European countries.

Consecutive pregnant women at <20 weeks of gestation with a body mass index (BMI) of ≥29 kg/m² and without GDM using the International Association of Diabetes and Pregnancy Study Group criteria (n = 436). For the intervention, women were randomized, stratified by site, to UC, HE, PA, or HE+PA. The women received 5 face-to-face and ≤4 telephone coaching sessions using the principles of motivational interviewing. A gestational weight gain (GWG) <5 kg was targeted. The coaches received standardized training and an intervention toolkit tailored to their culture and language.

The endpoints were the GWG at 35 to 37 weeks and the fasting glucose and insulin sensitivity [homeostasis model assessment insulin resistance (HOMA-IR)] at 24 to 28 weeks.

We randomized 108 women to HE+PA, 113 to HE, 110 to PA, and 105 to UC. In the HE+PA group, but not HE or PA alone, women achieved substantially less GWG than did the controls (UC) by 35 to 37 weeks (−2.02; 95% confidence interval, −3.58 to −0.46 kg). Despite this reduction, no improvements were seen in fasting or postload glucose levels, insulin concentrations, or HOMA-IR. The birthweights and large and small for gestational age rates were similar.

The combined HE+PA intervention was able to limit GWG but did not reduce fasting glycemia. Thus, lifestyle changes alone are unlikely to prevent GDM among women with a BMI of ≥29 kg/m².