Can Modest Changes in Lifestyle Prevent Gestational Diabetes?

Veronica Hackethal, MD

August 06, 2015

A new Finnish study, RADIEL, has found that modest changes in lifestyle could decrease the chance of high-risk pregnant women developing gestational diabetes mellitus (GDM) by about 39%. The findings were published online July 29 in Diabetes Care.

"Gestational diabetes can be prevented by a simple, easily applicable individualized lifestyle intervention in high-risk women," commented first author Saila Koivusalo, MD, of the University of Helsinki.

"The findings of the study may have major health consequences for both the mother and the child," she added.

Obesity affects up to 60% of reproductive-aged women in developed countries and increases the risk of pregnancy complications, including GDM, which in turn is well-known to increase future diabetes risk. Gestational diabetes and maternal obesity may also predispose the next generation to obesity and diabetes in later life, according to Dr Koivusalo.

These new findings contrast somewhat with those from other recent studies, including the UPBEAT trial and the pilot DALI study. Dr Koivusalo suggested this could be due to the targeting of the highest-risk patients only in RADIEL and the simplicity of the intervention. But the author of the DALI pilot study says the RADIEL trial shows a significant reduction in GDM only following "what appears to be a post hoc adjustment."

RADIEL Targets Highest-Risk Women

The RADIEL trial took place between February 2008 and January 2014 in three maternity hospitals in Helsinki, Finland. It included 293 pregnant women at less than 20 weeks gestation who had a history of GDM and/or had a prepregnancy body mass index (BMI) of 30 kg/m2 or more. Women were excluded if they already had GDM during the current pregnancy.

Researchers randomly assigned women to a behavioral intervention (n = 155) or standard prenatal care (n = 138). The intervention consisted of three individual counseling sessions about diet, physical activity, and weight control from trained study nurses and one group meeting with a dietician. Because the control group was also considered high risk, these women also received health advice about diet and physical activity.

"The main idea of the lifestyle advice provided [in the RADIEL study] was to be easily implemented and applicable to everyday life," Dr Koisuvalo explained.

The researchers diagnosed GDM based on a 75-g, 2-hour oral glucose tolerance test (OGTT) at 24 to 28 weeks gestation (fasting plasma glucose ≥ 5.3 mmol/L, 1-hour value ≥ 10.0 mmol/L, 2-hour value ≥ 8.6 mmol/L). Physical activity and food consumption were evaluated with self-reported questionnaires and a dietary index.

The final analysis included 269 women. The intervention group had a crude relative risk for GDM of 0.64 and a GDM incidence of 13.9% (n = 20). The control group had a GDM incidence of 21.6% (n = 27) (unadjusted = .097; P = .044 after adjustment for age, prepregnancy BMI, previous GDM, and number of weeks gestation.)

Between baseline and the second trimester, the intervention group had less gestational weight gain than the control group (2.5 kg vs 3.1 kg, respectively; mean difference, -0.58 kg, adjusted P = .037). From baseline to the third trimester, the mean difference was just -0.2 kg (adjusted P = 0.37).

Compared with controls, the intervention group also improved their diet and exercise (by about 15 minutes per week). Twenty-six percent of women in the intervention group met the physical activity goal of 150 minutes/week, while 23% of the control group did.

"We believe that in the RADIEL [trial] we have been able to identify a real high-risk group that is also the most likely to benefit from a lifestyle intervention during pregnancy," Dr Koivusalo and colleagues note.

The researchers did not see any differences between the groups in terms of other maternal or neonatal outcomes, however, but say that a larger sample size would have been needed to demonstrate this.

Conflicting Results

These new findings conflict with those of a recent UK study called the UPBEAT trial, which found that a behavioral intervention combining diet and exercise did not prevent GDM (Lancet Diabetes Endocrinol. 2015).

Comparisons between the UPBEAT and RADIEL trials may be hindered, however, by differences in methodology and in the groups of women included in the trials.

"I was rather surprised that glucose tolerance was not at all assessed in UPBEAT at baseline, which should be a standard procedure in a randomized controlled trial aiming at GDM prevention," Dr Koisuvalo pointed out, "Without this known, it is not possible to say anything about prevention of GDM."

The RADIEL trial excluded about 30% of women from participation because they already had GDM at the beginning of pregnancy. In contrast to RADIEL, participants in UPBEAT were more heterogeneous and only 3% to 4% had a previous history of GDM.

"In our study, 30% to 35% of the participants had a previous history of GDM, which we consider to be a very important risk factor for future GDM," explained Dr Koivusalo.

"According to previous type 2 diabetes prevention studies, the largest effect of a lifestyle intervention is observed in high-risk individuals," she added.

Moreover, the lifestyle strategies between RADIEL and UPBEAT may not be comparable.

"Our counseling was simple and thus also feasible," Dr Koivusalo pointed out, "The counseling in UPBEAT seems quite complicated, which might have influenced the results."

Key Is to Keep the Message Simple

Similarly, a pilot study for the DALI trial, though not large enough to look at GDM directly, suggested that a more complicated intervention combining healthy eating and exercise could "dilute" the message and produce less of an effect.

And David Simmons, MD, first author of the DALI pilot study and a professor of medicine at the University of Western Sydney, Australia, agrees that "UPBEAT was multiethnic, and [the pilot study for] DALI was international, making the 'reception'…and…delivery of the 'intervention' more complex."

Strengths of the RADIEL trial, according to Dr Simmons, include gestational weight gain in controls comparable to other studies; use of a standardized intervention; explicit inclusion of a high-risk group; and use of an OGTT at the beginning of the study.

On the other hand, the RADIEL trial did not use objective measures of lifestyle change except gestational weight gain, which showed a "trivial difference" between groups and suggested that the lifestyle change was "not substantial," Dr Simmons pointed out.

The RADIEL trial also used nonstandardized criteria for GDM, he continued, and showed no significant reduction in GDM before "what appears to be a post hoc adjustment."

The authors report no relevant financial relationships, as does Dr Simmons.

Diabetes Care. Published online July 29, 2015. Abstract

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