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Modified Dietary Interventions in Gestational Diabetes

Aug 4, 2018

Benefits seen for dietary interventions in gestational diabetes: birth weight and maternal glycemia are favorably influenced by dietary changes.

Gestational diabetes mellitus (GDM) is a common complication that affects many pregnancies worldwide. The mothers and babies are both at risk for developing long-term complications such as type 2 diabetes, obesity, and metabolic disorders. The mainstay of treatment for gestational diabetes is dietary and lifestyle modifications. This includes medical nutrition therapy, physical activity, and weight management. It is unknown whether dietary modifications are beneficial in preventing excessive fetal growth as well as achieving maternal euglycemia. In a systematic review and meta-analysis of randomized controlled trials, it was investigated whether modified dietary interventions in gestational diabetes, compared to a standard diet would improve neonatal outcomes as well as improve glycemia in women with gestational diabetes.

Several different databases were used to search for studies, including PubMed, MEDLINE, Cochrane Central Register of Controlled Trials, Embase, and ClinicalTrials.gov. The criteria for studies included: randomized controlled trials, women with GDM evaluated after dietary interventions, women with a pregnancy status of 2 weeks or more, ages 18-45 years old, and glucose intolerance or hyperglycemia during pregnancy. Studies were not included if participants had type 1 or type 2 diabetes. The primary outcomes included maternal glycemic outcomes such as mean glucose, fasting glucose, post-prandial glucose levels, HbA1c, and HOMA-IR. These parameters were compared to baseline values during assessments. Medication treatment such as oral diabetic medication and insulin and neonatal birth weight were also assessed.

A total of 126 articles were reviewed and 18 of these were used in the meta-analysis. This analysis included a total of 1,151 pregnant women with GDM. The type of dietary interventions included low glycemic index diet (n=4), DASH (n=3), low carbohydrate (n=3), fat modification (n=2), high fiber (n=1), energy restriction (n=1), soy-protein enriched (n=2), ethnic diets (n=1), and behavioral interventions (n=1). These trials were conducted in Spain, Australia, North America, and Europe and ran for a minimum of 2 weeks. Much of the trials had small sample sizes, and individuals were assessed on dietary adherence using food diaries. Women in the intervention groups were older than the women in the control group. The older participants also had higher post-prandial values and were most affected by the DASH and ethnic diets compared to the younger participants. Pooled risk ratios showed that of 18 studies, 1,023 women in 15 studies resulted in lower need of medication with the dietary modifications (RR 0.65 [95% CI: 0.47, 0.88]). There was a larger decrease in fasting, combined post-prandial, and post-breakfast glucose levels in the intervention group compared to the control group (p<0.02, p<0.007, and p<0.03 respectively). In 7 studies, there was no significant change in HbA1c, no change in HOMA-IR in 4 studies, and no significant change in post-lunch or post-dinner glucose in 2 studies.

Neonatal birth weight outcomes demonstrated positive results in the modified diet intervention group compared to the control group. The mean birth weight for the intervention group was 3,266.65 grams compared to 3,449.88 grams in the control group. Along with lower birth weights (-170.62g, p<0.04), there was also less macrosomia in the intervention group (p<0.02). Based on the type of diets tested, pooled analysis showed that low-GI diets had lower fasting blood glucose, as well as post-prandial, and post-breakfast glucose levels. The DASH diet showed the same results and also reductions in HOMA-IR, HbA1c, medication need, and macrosomia.

Pooled analysis of the soy-enriched diet showed a decrease in medication use and birth weight. The behavioral modification study showed significant differences in HbA1c, and post-prandial glucose. The ethnic diets showed significant changes in post-prandial glucose and fasting glucose. All other diets had no significant changes in any parameters of the primary outcomes.

After reviewing all these studies, it is evident that diet plays a major role in the outcomes of gestational diabetes.  Modified dietary interventions in gestational diabetes have shown to reduce medication use, which is desired by all parties during pregnancy. With a controlled diet, patients with gestational diabetes can better manage their glucose, prevent macrosomia, and have better overall neonatal outcomes. There is an urgent need to implement a well-designed diet based on nutrient quality and quantity for patients with gestational diabetes mellitus.

Practice Pearls:

  • Gestational Diabetes Mellitus (GDM) is a common complication that affects many pregnancies worldwide.
  • With diet modifications, patients who are pregnant can achieve euglycemia and have better neonatal outcomes such as normal birth weights.
  • Along with the prevention of macrosomia, dietary modifications can prevent the short- and long-term risks associated with gestational diabetes.

Reference for dietary interventions in gestational diabetes:

Yamamoto, Jennifer M., et al. “Gestational Diabetes Mellitus and Diet: A Systematic Review and Meta-Analysis of Randomized Controlled Trials Examining the Impact of Modified Dietary Interventions on Maternal Glucose Control and Neonatal Birth Weight.” Diabetes Care, vol. 41, no. 7, 2018, pp. 1346–1361., doi:10.2337/dc18-0102.

Amanda Cortes, 2019 LECOM School of Pharmacy PharmD Candidate