Objective To summarize short term outcomes in randomized controlled trials comparing glibenclamide or metformin versus insulin or versus each other in women with gestational diabetes requiring drug treatment. Design Systematic review and meta-analysis. Eligibility criteria for selecting studies Randomized controlled trials that fulfilled all the following: (1) published as full text; (2) addressed women with gestational diabetes requiring drug treatment; (3) compared glibenclamide v insulin, metformin v insulin, or metformin v glibenclamide; and (4) provided information on maternal or fetal outcomes. Data sources Medline, CENTRAL, and Embase were searched up to 20 May 2014. Outcomes measures We considered 14 primary outcomes (6 maternal, 8 fetal) and 16 secondary (5 maternal, 11 fetal) outcomes. Results We analyzed 15 articles, including 2509 subjects. Significant differences for primary outcomes in glibenclamide v insulin were obtained in birth weight (mean difference 109 g (95% confidence interval 35.9 to 181)), macrosomia (risk ratio 2.62 (1.35 to 5.08)), and neonatal hypoglycaemia (risk ratio 2.04 (1.30 to 3.20)). In metformin v insulin, significance was reached for maternal weight gain (mean difference −1.14 kg (−2.22 to −0.06)), gestational age at delivery (mean difference −0.16 weeks (−0.30 to −0.02)), and preterm birth (risk ratio 1.50 (1.04 to 2.16)), with a trend for neonatal hypoglycaemia (risk ratio 0.78 (0.60 to 1.01)). In metformin v glibenclamide, significance was reached for maternal weight gain (mean difference −2.06 kg (−3.98 to −0.14)), birth weight (mean difference −209 g (−314 to −104)), macrosomia (risk ratio 0.33 (0.13 to 0.81)), and large for gestational age newborn (risk ratio 0.44 (0.21 to 0.92)). Four secondary outcomes were better for metformin in metformin v insulin, and one was worse for metformin in metformin v glibenclamide. Treatment failure was higher with metformin than with glibenclamide. Conclusions At short term, in women with gestational diabetes requiring drug treatment, glibenclamide is clearly inferior to both insulin and metformin, while metformin (plus insulin when required) performs slightly better than insulin. According to these results, glibenclamide should not be used for the treatment of women with gestational diabetes if insulin or metformin is available. Systematic review registration NCT01998113

OBJECTIVE Medical nutrition therapy is a mainstay of gestational diabetes mellitus (GDM) treatment. However, data are limited regarding the optimal diet for achieving euglycemia and improved perinatal outcomes. This study aims to investigate whether modified dietary interventions are associated with improved glycemia and/or improved birth weight outcomes in women with GDM when compared with control dietary interventions. RESEARCH DESIGN AND METHODS Data from published randomized controlled trials that reported on dietary components, maternal glycemia, and birth weight were gathered from 12 databases. Data were extracted in duplicate using prespecified forms. RESULTS From 2,269 records screened, 18 randomized controlled trials involving 1,151 women were included. Pooled analysis demonstrated that for modified dietary interventions when compared with control subjects, there was a larger decrease in fasting and postprandial glucose (−4.07 mg/dL [95% CI −7.58, −0.57]; P = 0.02 and −7.78 mg/dL [95% CI −12.27, −3.29]; P = 0.0007, respectively) and a lower need for medication treatment (relative risk 0.65 [95% CI 0.47, 0.88]; P = 0.006). For neonatal outcomes, analysis of 16 randomized controlled trials including 841 participants showed that modified dietary interventions were associated with lower infant birth weight (−170.62 g [95% CI −333.64, −7.60]; P = 0.04) and less macrosomia (relative risk 0.49 [95% CI 0.27, 0.88]; P = 0.02). The quality of evidence for these outcomes was low to very low. Baseline differences between groups in postprandial glucose may have influenced glucose-related outcomes. As well, relatively small numbers of study participants limit between-diet comparison. CONCLUSIONS Modified dietary interventions favorably influenced outcomes related to maternal glycemia and birth weight. This indicates that there is room for improvement in usual dietary advice for women with GDM.

Background: Gestational diabetes mellitus (GDM) is an increasing problem world-wide. Lifestyle interventions and/or vitamin D supplementation might help prevent GDM in some women. Methods/design: Pregnant women at risk of GDM (BMI≥29 (kg/m²)) from 9 European countries will be invited to participate and consent obtained before 19+6 weeks of gestation. After giving informed consent, women without GDM will be included (based on IADPSG criteria: fasting glucose<5.1mmol; 1 hour glucose <10.0 mmol; 2 hour glucose <8.5 mmol) and randomized to one of the 8 intervention arms using a 2×(2×2) factorial design: (1) healthy eating (HE), 2) physical activity (PA), 3) HE+PA, 4) control, 5) HE+PA+vitamin D, 6) HE+PA+placebo, 7) vitamin D alone, 8) placebo alone), pre-stratified for each site. In total, 880 women will be included with 110 women allocated to each arm. Between entry and 35 weeks of gestation, women allocated to a lifestyle intervention will receive 5 face-to-face, and 4 telephone coaching sessions, based on the principles of motivational interviewing. The lifestyle intervention includes a discussion about the risks of GDM, a weight gain target <5kg and either 7 healthy eating ‘messages’ and/or 5 physical activity ‘messages’ depending on randomization. Fidelity is monitored by the use of a personal digital assistance (PDA) system. Participants randomized to the vitamin D intervention receive either 1600 IU vitamin D or placebo for daily intake until delivery. Data is collected at baseline measurement, at 24–28 weeks, 35–37 weeks of gestation and after delivery. Primary outcome measures are gestational weight gain, fasting glucose and insulin sensitivity, with a range of obstetric secondary outcome measures including birth weight. Discussion: DALI is a unique Europe-wide randomised controlled trial, which will gain insight into preventive measures against the development of GDM in overweight and obese women. Trial registration: ISRCTN70595832

As vitamin D deficiency is associated with an increased risk of gestational diabetes mellitus (GDM), we aimed to test vitamin D supplementation as a strategy to reduce GDM risk (evaluated after fasting plasma glucose (FPG), insulin resistance and weight gain) in pregnant overweight/obese women. The DALI vitamin D multicenter study enrolled women with prepregnancy body mass index (BMI) ≥ 29 kg/m2, ≤19 + 6 weeks of gestation and without GDM. Participants were randomized to receive 1600 IU/day vitamin D3 or placebo (each with or without lifestyle intervention) on top of (multi)vitamins supplements. Women were assessed for vitamin D status (sufficiency defined as serum 25-hydroxyvitamin D (25(OH)D) ≥ 50 nmol/l), FPG, insulin resistance and weight at baseline, 24-28 and 35-37 weeks. Linear or logistic regression analyses were performed to assess intervention effects. Average baseline serum 25(OH)D was ≥50 nmol/l across all study sites. In the vitamin D intervention arm (n = 79), 97% of participants achieved target serum vitamin 25(OH)D (≥50 nmol/l) at 24-28 weeks and 98% at 35-37 weeks vs 74% and 78% respectively in the placebo arm (n = 75, p < 0.001). A small but significantly lower FPG (-0.14 mmol/l; CI95 -0.28, -0.00) was observed at 35-37 weeks with the vitamin D intervention without any additional difference in metabolic status, perinatal outcomes or adverse event rates. In the DALI vitamin D trial, supplementation with 1600 IU vitamin D3/day achieved vitamin D sufficiency in virtually all pregnant women and a small effect in FPG at 35-37 weeks. The potential of vitamin D supplementation for GDM prevention in vitamin D sufficient populations appears to be limited. ISRCTN70595832.