Reducing the Risk of Gestational Diabetes

There are plenty of good reasons to decrease the risk of gestational diabetes mellitus (GDM). The condition can increase the risk of more severe complications of pregnancy, like preeclampsia, hypertension, premature birth, caesarian section, and fetal loss. In addition, women with GDM and their offspring are at increased risk of developing type 2 diabetes later in life.

Reducing weight during pregnancy can help fend off GDM, but the research is murky about how best to achieve this purpose. Do lifestyle interventions really make a difference? If so, what’s best: nutrition, exercise, or both?

A recent Cochrane Review of randomized controlled trials (RCTs) published up to February 2014 looked at this issue.¹ Results showed “no clear” difference in the development of GDM between women who received combined diet and exercise interventions, vs those who did not (average risk ratio (RR) 0.92, 95% confidence interval (CI) 0.68 to 1.23; 11 trials, 3744 women). The review concluded that not enough conclusive evidence is available to guide practice.

One of the issues may be that more complicated multi-pronged interventions may be difficult to implement or follow. Trying to change several aspects of one’s behavior all at once can be overwhelming, and lead to less favorable results.

Results from one of the largest RCTs to date on this issue seem to bear this out. Known as the UK Pregnancies Better Eating and Activity (UPBEAT) trial, the study included 1555 pregnant women at risk for GDM (mean BMI 36.3 kg/m²).² Researchers randomized women to an intensive combined diet and exercise intervention (n=783), or standard care (n=772). Results showed no significant differences in the incidence of GDM between the two groups (P=0.68).

Likewise, a pilot study from the European Vitamin D and Lifestyle Intervention for GDM Prevention (DALI) trial found that a more complicated intervention combining diet and exercise did not improve blood glucose control, though the study could not directly assess GDM.³ The DALI pilot took place in nine European countries and included 150 pregnant women at risk for GDM (BMI ≥ 29 kg/m²) who were randomized to a healthy diet intervention, increased physical activity, or both. 

Contrasting findings, though, come from the Finnish Gestational Diabetes Prevention Study (RADIEL) trial, and suggest that a less ambitious program may help certain groups of women.⁴ The RADIEL trial included 293 high risk women with a history of GDM and/or a prepregnancy BMI of at least 30 kg/m². Women were randomized to a moderate lifestyle intervention (healthy eating, physical activity, and weight control, n=155), or standard care (n=138). Results showed that the intervention group had 39% decreased risk of developing GDM, and significantly less gestational weight gain (P=0.037) compared to standard care.

Perhaps in an effort to find the simplest, easiest intervention, some studies have tried to tease out which is more important in reducing risk for GDM – diet alone or exercise alone?

Interestingly, the DALI pilot found that near the end of pregnancy (35-37 weeks’ gestation), the healthy diet group had significantly less gestational weight gain (P=0.02), and significantly lower fasting glucose (P=0.01) compared to baseline than the physical activity group.

A recent review supports these findings. The review included 34 observational and case-control studies published up to January 2015. Results showed higher risk for GDM among women who ate diets high in fat, cholesterol, and red and processed meats, supporting current guidelines about eating more fruits, vegetables, whole grains, and fish, as well as less red and processed meat, refined grains, and high fat dairy.⁵

On the other hand, a recent metanalysis suggests that exercise is the key.⁶ The study included 13 randomized controlled trials covering 2873 pregnant, formerly inactive women. Results showed that moderate exercise during pregnancy decreased the risk of GDM by 31% (relative risk [RR], 0.69; 95% confidence interval [CI], 0.52 - 0.91; P=0.009). Although the study did not include information on birth outcomes, the results turn more traditional notions about the harmful effects of exercise during pregnancy on their head.

The results also support a recommendation from the American College of Obstetricians and Gynecologists, advising pregnant women to engage in moderate exercise for 30 minutes per day, most days of the week.⁷

Because of differences in methodologies and variations in study populations, comparing trials like these can be like comparing apples to oranges. At the end of the day, however, the results do make a certain amount of sense. They seem to uphold current recommendations about physical activity and improved nutrition during pregnancy. They also seem to point to the reasonable conclusion that finding a simple, easy-to-follow plan that fits into a woman’s lifestyle may help decrease her risk of GDM. People will take the path of least resistance, and finding that path may be an individual choice.

Take-home Points

• Studies suggest that intensive behavioral interventions that combine diet and exercise may be too difficult to follow, and may not have much of an impact on decreasing GDM risk.

• A recent large RCT has suggested that a less intensive lifestyle intervention that combines diet and exercise may be helpful.

• There is conflicting evidence about whether interventions that target diet alone or exercise alone can help decrease the risk of GDM.

• Research seems to support current recommendations about improving diet and physical activity during pregnancy.

References:

1. Bain E, et al. Diet and exercise interventions for preventing gestational diabetes mellitus. Cochrane Database Syst Rev. 2015 Apr 12;4:CD010443.

2. Poston L, et al. Effect of a behavioural intervention in obese pregnant women (the UPBEAT study): a multicentre, randomised controlled trial. Lancet Diabetes Endocrinol. 2015 Oct;3(10):767-777.

3. Simmons D, et al. Results from a European Multicenter Randomized Trial of Physical Activity and/or Healthy Eating to Reduce the Risk of Gestational Diabetes Mellitus: The DALI Lifestyle Pilot. Diabetes Care. 2015 Sep;38(9):1650-1656.

4. Koivusalo SB, et al. Gestational diabetes mellitus can be prevented by lifestyle intervention: the Finnish Gestational Diabetes Prevention Study (RADIEL): a randomized controlled trial. Diabetes Care. 2016 Jan;39(1):24-30.

5. Schoenaker DA, et al. The role of energy, nutrients, foods, and dietary patterns in the development of gestational diabetes mellitus: a systematic review of observational studies. Diabetes Care. 2016 Jan;39(1):16-23.

6. Sanabria-Martínez G, et al. Effectiveness of physical activity interventions on preventing gestational diabetes mellitus and excessive maternal weight gain: a meta-analysis. BJOG. 2015 Aug;122(9):1167-1174.

7. ACOG. Exercise during pregnancy. Accessed on March 21, 2016 at http://www.acog.org/Patients/FAQs/Exercise-During-Pregnancy.