MAIN STUDY: Low Glycaemic Index (GI) Diet in the Management of GDM SUB-STUDY: The Breast Milk Sub-Study (GIinGDM)

• MAIN STUDY: Percentage of postprandial self monitored blood glucose (SMBG) values within the target range [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization to delivery. The endpoint is a single value for each participant - namely the percentage of all the postprandial SMBG values within the target range recommended by the Canadian Diabetes Association (5.0 to 6.6 mmol/L)
• SUB-STUDY (n=75): Oxygen Radical Absorbance Capacity (ORAC) (Antioxidant Capacity) of transitional and mature breast milk. [ Time Frame: 1 week and 8 weeks postpartum ] [ Designated as safety issue: No ]
  Breast milk samples (25 mL) will be collected 1 week and 8 weeks after birth from a complete breast milk collection. Measures will be compared between and within groups.

• MAIN STUDY: Infant birth weight [ Time Frame: At delivery ] [ Designated as safety issue: No ]
  Weight of the baby at delivery in grams.
• MAIN STUDY: Percentage of self-monitored fasting glucose values within the target range [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the start of the intervention to delivery. The endpoint is a single value for each participant - namely the percentage of all the fasting SMBG values within the target range recommended by the Canadian Diabetes Association (3.8 to 5.2 mmol/L)
• MAIN STUDY: Glucose variability [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization to delivery. This endpoint is the coefficient of variation of all the SMBG values obtained (CV = 100*SD/mean), where SD is standard deviation; a single value for each participant.
• MAIN STUDY: Insulin prescription incidence [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  Proportion of women prescribed insulin during the intervention
• MAIN STUDY: Mean fasting glucose [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization to delivery. The endpoint is the mean of all fasting SMBG values obtained - a single value for each participant.
• MAIN STUDY: Mean postprandial glucose [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization to delivery. This endpoint is the mean of all postprandial SMBG values obtained; a single value for each participant.
• MAIN STUDY: Mean post-breakfast glucose [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization to delivery. This endpoint is the mean of all SMBG values 2 hours after breakfast; a single value in each participant.
• MAIN STUDY: Mean post-lunch blood glucose [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization to delivery. This endpoint is the mean of all SMBG values 2 hours after lunch; a single value in each participant.
• MAIN STUDY: Mean post-dinner blood glucose [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization to delivery. This endpoint is the mean of all SMBG values 2 hours after dinner; a single value in each participant.
• MAIN STUDY: Change in LDL oxidation at 4 weeks [ Time Frame: Change from randomization in LDL oxidation at 4 weeks. ] [ Designated as safety issue: No ]
  Difference between LDL oxidation measured in fasting venous blood at randomization and 4 weeks.
• MAIN STUDY: LDL oxidation 6-8 weeks after delivery [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  LDL oxidation measured in fasting venous blood 6-8 weeks after delivery.
• MAIN STUDY: Change in Oxygen Radical Absorbance Capacity (ORAC) of plasma at 4 weeks [ Time Frame: Change from randomization to 4 weeks ] [ Designated as safety issue: No ]
  Difference in Oxygen Radical Absorbance Capacity (ORAC) of plasma measured in venous serum at randomization and 4 weeks.
• MAIN STUDY: Change in c-reactive protein (CRP) at 4 weeks [ Time Frame: Change in CRP from randomization at 4 weeks ] [ Designated as safety issue: No ]
  Difference in c-reactive protein concentration in venous serum from baseline at 4 weeks.
• MAIN STUDY: Post-partum CRP [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Concentration of venous serum c-reactive protein 6-8 weeks after delivery.
• MAIN STUDY: Post-partum fasting serum glucose [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Venous fasting serum glucose 6-8 weeks after delivery
• MAIN STUDY: Post-partum serum glucose concentration 2 hours after consumption of 75g oral glucose (2hrPC serum glucose). [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Venous serum glucose concentration 2 hours after consumption of 75g oral glucose (oral glucose tolerance test).
• MAIN STUDY: Incidence of post-partum impaired glucose tolerance [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Proportion of women with venous serum glucose concentration 2 hours after a 75g oral glucose tolerance test between 7.8 and 11.0 mmol/L, inclusive.
• MAIN STUDY: Incidence of post-partum diabetes mellitus [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Proportion of women with diabetes 6-8 weeks after delivery. Diabetes is defined as fasting serum glucose greater than or equal to 7.0 mmol/L and/or serum glucose 2 hours after 75g oral glucose tolerance test greater than or equal to 11.1mmol/L.
• MAIN STUDY: Maternal weight gain [ Time Frame: From pre-pregnancy to delivery: up to 9 months ] [ Designated as safety issue: No ]
  Difference between reported pre-pregnancy body weight and last body weight measured before delivery.
• MAIN STUDY: Rate of maternal weight gain [ Time Frame: From randomization to delivery ] [ Designated as safety issue: No ]
  Difference between maternal body weight at randomization and last body weight measured before delivery divided by the number of weeks between the measurements.
• MAIN STUDY: Change in infant weight [ Time Frame: Change in infant body weight from birth to 6- 8 weeks ] [ Designated as safety issue: No ]
  Difference between infant birthweight and weight 6-8 weeks after delivery.
• MAIN STUDY & SUB-STUDY (n=75): Maternal dietary intake [ Time Frame: From randomization to 6- 8 weeks post-partum ] [ Designated as safety issue: No ]
  Dietary analysis will be conducted using software containing the Canadian Nutrient File, supplemented with data that used standardized GI testing methodology. Comparison will be made between and within groups.
• SUB-STUDY (n=75): Concentration of vitamin C, E, and Beta-carotene in transitional breast milk [ Time Frame: 1 week after delivery ] [ Designated as safety issue: No ]
  Concentration of vitamin C, vitamin E and beta-carotene in breast milk collected 1 week after delivery. Comparison will be made between and within study groups.
• SUB-STUDY (n=75): Concentration of vitamin C, E, and Beta-carotene in mature breast milk [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Concentration of vitamin C, vitamin E and beta-carotene in breast milk collected 6-8 weeks after delivery. Comparison will be made between and within study groups.
• MAIN STUDY: Infant demographics [ Time Frame: Delivery to 6-8 weeks postpartum ] [ Designated as safety issue: No ]
  Collection of infant demographics, such as gestational age at birth, sex, incidence and type of complications as noted in maternal or infant chart, mode of delivery, length of stay in hospital
• MAIN STUDY: Change in infant body measurements from birth to 6-8 weeks post-partum [ Time Frame: Change in infant body measurements from delivery to 6-8 weeks post-partum ] [ Designated as safety issue: No ]
  Weight, head circumference, and height/length
• MAIN STUDY: Infant APGAR score at delivery [ Time Frame: Delivery ] [ Designated as safety issue: No ]
  Infant APGAR score at delivery as recorded in maternal medical chart.
• MAIN STUDY: Change in maternal blood pressure and resting pulse from randomization to 4 weeks [ Time Frame: Change from randomization to 4 weeks. ] [ Designated as safety issue: No ]
  Difference between maternal blood pressure and resting pulse from randomization at4 weeks.
• MAIN STUDY: Maternal blood pressure and resting pulse at 6-8 weeks post-partum [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Maternal blood pressure and resting pulse at 6-8 weeks post-partum.
• MAIN STUDY: Infant waist circumference at 6-8 weeks [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Infant waist circumference at 6-8 weeks.
• MAIN STUDY: Change in ultrasound measurements from randomization to delivery. [ Time Frame: Change from randomization to delivery ] [ Designated as safety issue: No ]
  Difference between infant ultrasound measurements (Bi-parietal diameter, head circumference, abdominal circumference, and femur length) from baseline to delivery.
• MAIN STUDY: Maternal height at baseline [ Time Frame: Baseline ] [ Designated as safety issue: No ]
  Maternal height at baseline
• MAIN STUDY: Maternal medical history [ Time Frame: Baseline ] [ Designated as safety issue: No ]
  Maternal medical history
• MAIN STUDY: Maternal medical complications from baseline to 6-8 weeks post-partum [ Time Frame: Baseline to 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Incidence and type of maternal medical complications from baseline to 6-8 weeks post-partum
• MAIN STUDY: Change in maternal weight from delivery at 6-8 weeks post-partum [ Time Frame: Difference between delivery and 6-8 weeks post-partum ] [ Designated as safety issue: No ]
  Difference in maternal weight from delivery at 6-8 weeks postpartum.
• MAIN STUDY: Maternal pre-natal demographic information [ Time Frame: Baseline ] [ Designated as safety issue: No ]
  Maternal pre-natal demographic information (e.g. ethnicity, language used at home, household food preparation and purchasing, education obtained, employment status, treatment of diabetes, prior exposure to a registered dietitian, cigarette, recreational drug, and alcohol use before and during pregnancy, and physical activity) using a pre-tested, face-validated questionnaire.
• MAIN STUDY: Maternal post-partum socio-demographic data related to infant feeding practices [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Socio-demographic factors previously identified in the literature as affecting infant feeding practices; including access to breastfeeding education while in hospital.
• MAIN STUDY: Length of time between delivery and maternal breast fullness [ Time Frame: Time after delivery ] [ Designated as safety issue: No ]
  Length of time between delivery and maternal breast fullness.
• MAIN STUDY: Change in conjugated dienes at 4 weeks [ Time Frame: change from baseline to 4 weeks. ] [ Designated as safety issue: No ]
  Difference between conjugated dienes of plasma measured in venous serum at baseline and 4 weeks.
• MAIN STUDY: Conjugated dienes post-partum [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Conjugated dienes in fasting venous blood 6-8 weeks after delivery
• MAIN STUDY: Oxygen Radical Absorbance Capacity (ORAC) of venous plasma post-partum [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  ORAC measured in fasting venous blood 6-8 weeks after delivery
• MAIN STUDY: Change in full lipid profile at 4 weeks [ Time Frame: Change in full lipid profile of plasma from baseline at 4 weeks ] [ Designated as safety issue: No ]
  Difference in full lipid profile of fasting venous blood at baseline and 4 weeks.
• MAIN STUDY: Full lipid profile post-partum [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Full lipid profile of fasting venous blood at 6-8 weeks post-partum
• MAIN STUDY: Change in incidence and severity of symptoms from baseline to 6-8 weeks postpartum [ Time Frame: Change from baseline to 6-8 weeks postpartum ] [ Designated as safety issue: No ]
  Difference in the incidence and severity of maternal symptoms present from baseline to 6-8 weeks postpartum using a standardised questionnaire.
• MAIN STUDY: Infant feeding practices [ Time Frame: 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Maternal infant feeding practices from delivery to 6-8 weeks postpartum
• MAIN STUDY: Participant satisfaction of baseline education class [ Time Frame: Baseline ] [ Designated as safety issue: No ]
  Participant reactions and opinions on baseline education class using a face-validated, pre-tested questionnaire.
• MAIN STUDY: Change in participant knowledge of GI from baseline to 6-8 weeks after delivery [ Time Frame: Change in GI knowledge from randomization to 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Difference in participant knowledge of GI from randomization pre-education class) to 6-8 weeks after delivery using a face-validated, pre-tested questionnaire.
• MAIN STUDY: Participant knowledge of GI at baseline [ Time Frame: Baseline ] [ Designated as safety issue: No ]
  Participant knowledge of GI at baseline (pre-education class)using a validated questionnaire.
• MAIN STUDY: Change in participant opinion on availability and acceptability of study diet foods [ Time Frame: Change in opinion from 2 weeks to 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Difference in participant opinion on availability and acceptability of study diet foods from 2 weeks to 6-8 weeks after delivery using a validated questionnaire.
• MAIN STUDY: Difference in dietary GI between study groups. [ Time Frame: From baseline to 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Difference in dietary GI between study groups from baseline to 6-8 weeks post delivery using a short-form semi-quantitative food frequency questionnaire (FFQ). The FFQ collects dietary intake data on the 3 months preceding administration. The FFQ has been standardised and evaluated for readability by nutrition professionals, clinicians and/or researchers with experience in surveying, and has been face-validated and pre-tested.
• MAIN STUDY: Change in behaviour from baseline (pre-class) to 6-8 weeks after delivery. [ Time Frame: Change in behaviour from baseline (pre-class) to 6-8 weeks after delivery ] [ Designated as safety issue: No ]
  Difference in behaviour within and between groups from baseline (pre-class) to 6-8 weeks after delivery using face-validated, pre-tested questionnaires, including a short-form semi-quantitative food frequency questionnaire (FFQ). The FFQ collects dietary intake data on the 3 months preceding administration. The FFQ has been standardised and evaluated for readability by nutrition professionals, clinicians and/or researchers with experience in surveying.

• Infant birth weight [ Time Frame: At delivery ] [ Designated as safety issue: No ]
  Weight of the baby at delivery in grams.
• Percentage of self-monitored fasting glucose values within the target range [ Time Frame: From randomization to delivery: up to 16 weeks ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the start of the intervention (26-28 weeks gestation) to delivery (38-42 weeks gestation). The endpoint is a single value for each participant - namely the percentage of all the fasting SMBG values within the target range recommended by the Canadian Diabetes Association (3.8 to 5.2 mmol/L)
• Glucose variability [ Time Frame: From randomization to delivery: up to 16 weeks ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization(26-28 weeks gestation) to delivery (38-42 weeks gestation). This endpoint is the coefficient of variation of all the SMBG values obtained (CV = 100*SD/mean); a single value for each participant.
• Insulin prescription [ Time Frame: From randomization to delivery: up to 16 weeks ] [ Designated as safety issue: No ]
  Proportion of women prescibed insulin during the intervention
• Mean fasting glucose [ Time Frame: From randomization to delivery: up to 16 weeks ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization(26-28 weeks gestation) to delivery (38-42 weeks gestation). The endpoint is the mean of all fasting SMBG values obtained - a single value for each participant.
• Mean postprandial glucose [ Time Frame: From randomization to delivery: up to 16 weeks ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization(26-28 weeks gestation) to delivery (38-42 weeks gestation). This endpoint is the mean of all postprandial SMBG values obtained; a single value for each participant.
• Mean post-breakfast glucose [ Time Frame: From randomization to delivery: up to 16 weeks ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization(26-28 weeks gestation) to delivery (38-42 weeks gestation). This endpoint is the mean of all SMBG values 2 hours after breakfast; a single value in each participant.
• Mean post-lunch blood glucose [ Time Frame: From randomization to delivery: up to 16 weeks ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization(26-28 weeks gestation) to delivery (38-42 weeks gestation). This endpoint is the mean of all SMBG values 2 hours after lunch; a single value in each participant.
• Mean post-dinner blood glucose [ Time Frame: From randomization to delivery: up to 16 weeks ] [ Designated as safety issue: No ]
  SMBG values are obtained 4 times daily (1 fasting and 3 postprandial) throughout the study from the randomization(26-28 weeks gestation) to delivery (38-42 weeks gestation). This endpoint is the mean of all SMBG values 2 hours after dinner; a single value in each participant.
• Change in LDL oxidation at 4 weeks [ Time Frame: Change from baseline in LDL oxidation at 4 weeks. ] [ Designated as safety issue: No ]
  Difference between LDL oxidation measured in fasting blood at baseline and 4 weeks.
• LDL oxidation post-partum [ Time Frame: 8 weeks after delivery ] [ Designated as safety issue: No ]
  LDL oxidation measured in fasting blood 8 weeks after delivery.
• Change in total antioxidant capacity of plasma at 4 weeks [ Time Frame: Change in total antioxidant capacity of plasma from baseline to 4 weeks ] [ Designated as safety issue: No ]
  Difference in total antioxidant capacity of plasma measured in serum at baseline and 4 weeks.
• Total antioxidant capacity of plasma post-partum [ Time Frame: 8 weeks after delivery ] [ Designated as safety issue: No ]
  Total antioxidant capacity of plasma measured in serum 8 weeks after delivery
• Change in CRP at 4 weeks [ Time Frame: Change from baseline in CRP at 4 weeks ] [ Designated as safety issue: No ]
  Difference in c-reactive protein concentration in serum at baseline and 4 weeks.
• Post-partum CRP [ Time Frame: 8 weeks after delivery ] [ Designated as safety issue: No ]
  Concentration of serum c-reactive protein 8 weeks after delivery.
• Post-partum fasting serum glucose [ Time Frame: 8 weeks after delivery ] [ Designated as safety issue: No ]
  Fasting serum glucose 8 weeks after delivery
• Post-partum 2hrPC serum glucose [ Time Frame: 8 weeks after delivery ] [ Designated as safety issue: No ]
  Serum glucose concentration 2 hours after consumption of 75g oral glucose (oral glucose tolerance test).
• Incidence of post-partum impaired glucose tolerance [ Time Frame: 8 weeks after delivery ] [ Designated as safety issue: No ]
  Proportion of women with serum glucose concentration 2 hours after a 75g oral glucose tolerance test between 7.8 and 11.0 mmol/L, inclusive.
• Incidence of post-partum diabetes mellitus [ Time Frame: 8 weeks after delivery ] [ Designated as safety issue: No ]
  Proportion of women with diabetes 8 weeks after delivery. Diabetes is defined as fasting serum glucose greater than or equal to 7.0 mmol/L and/or serum glucose 2 hours after 75g oral glucose tolerance test greater than or equal to 11.1mmol/L.
• Maternal weight gain [ Time Frame: From pre-pregnancy to delivery: up to 9 months ] [ Designated as safety issue: No ]
  Difference between reported pre-pregnancy body weight and last body weight measured before delivery.
• Rate of maternal weight gain [ Time Frame: From randomization to delivery: up to 16 weeks ] [ Designated as safety issue: No ]
  Difference between maternal body weight at randomization and last body weight measured before delivery divided by the number of weeks between the measurements.
• Change in infant weight [ Time Frame: Change from birthweight in infant body weight at 8 weeks ] [ Designated as safety issue: No ]
  Difference between infant birthweight and weight 8 weeks after delivery.

MAIN STUDY: Low glycaemic index (GI) diets are recommended by the Canadian Diabetes Association for treating type 1 and 2 diabetes mellitus (DM), but the role of GI in the management of gestational diabetes(GDM)is not yet clear. The main purpose of this study is to determine the effect of a low GI diet on blood sugar control in women with GDM. The effect of a low GI diet on maternal oxidative stress, pregnancy and delivery outcomes and markers of risk for diabetes after birth in both the mother and baby will also be assessed. SUB-STUDY: The main purpose of the sub-study is to determine if the breast milk (BM) of women with GDM consuming a low GI diet will have a higher antioxidant capacity than the BM of women receiving a medium-high GI diet (control/standard care). The effect of a low glycaemic index diet on maternal dietary intake of specific nutrient-antioxidants (i.e. vitamin C, E, and beta-carotene) (prenatal and postpartum) and concentration of vitamin C, E, and beta-carotene in participants' transitional and mature BM will also be assessed. The ORAC (Oxygen radical absorbance capacity) assay will be used to assess overall antioxidant capacity.

Hypothesis:

MAIN: The use of low-GI foods in the management of GDM reduces postprandial BG and oxidative stress; thereby reducing maternal and infant perinatal complications.

Hypothesis: Breast milk (BM) of women with GDM consuming a low GI diet will have higher BM antioxidant than women receiving the medium to high GI diet.

MAIN STUDY: Use of low GI education is currently accepted by the Canadian Diabetes Association in treatment of type 1 and 2 DM, but is not included in the clinical practice guidelines(CPG) for management of GDM. Data collected to date support use of low GI in treatment of GDM, but more data are needed to influence CPG. In this study the effect of a low GI diet on maternal and neonatal markers of glycaemic control and postpartum diabetes risk in mother and baby will be determined. This study will also assess the role that maternal oxidative stress may play in this relationship.

Hypothesis: The use of low-GI foods in the management of GDM reduces postprandial BG and oxidative stress; thereby reducing maternal and infant perinatal complications.

SUB-STUDY: Breast milk (BM) is accepted as the optimal source of nutrition for infants. A wealth of literature on BM composition exists. This work includes measurement of antioxidants in BM. Women diagnosed with gestational hyperglycaemia have decreased antioxidant capacity in comparison to normoglycaemic pregnant women. A direct relationship exists between postprandial glycaemic response and oxidative stress. Low GI carbohydrate is converted to blood glucose (BG) more slowly than medium to high GI carbohydrate

Hypothesis: Breast milk (BM) of women with GDM consuming a low GI diet will have higher BM antioxidant than women receiving the medium to high GI diet.

• Other: Standard Care
  Standard dietary advice for women with GDM with special emphasis on use of high fiber or whole grain carbohydrate foods with a medium to high GI. What's on Your Plate? and 3-dimensional food models will be used to teach servings size and meal planning. This groups will be provided with food substitution lists (key-foods method) composed of medium to high GI foods.
  Other Names:

  • medium to high Glycaemic Index
  • standard care
• Other: Low GI diet
  Nutrition education according to standard care similar to the control group with supplementary GI-education. GI-education will be taught using the "Stop-Light-Method". This groups will be provided with food substitution lists (key-foods method) composed of low-GI carbohydrate-containing food. The GI-education tool(s) will build on standard care education where patients are taught which food groups contain carbohydrate.
  Other Names:

  • glycemic index
  • glycaemic index
  • low glycemic carbohydrates
  • low glycaemic carbohydrates

• Placebo Comparator: Standard Care
  Standard care dietary advice to emphasize high fiber foods with a moderate to high GI
  Intervention: Other: Low GI diet
• Experimental: Low GI Diet
  Low GI dietary advice in addition to standard care
  Intervention: Other: Standard Care

• Ceriello A. Acute hyperglycaemia and oxidative stress generation. Diabet Med. 1997 Aug;14 Suppl 3:S45-9. Review.
• Ceriello A. The emerging role of post-prandial hyperglycaemic spikes in the pathogenesis of diabetic complications. Diabet Med. 1998 Mar;15(3):188-93. Review.
• Huang D, Ou B, Prior RL. The chemistry behind antioxidant capacity assays. J Agric Food Chem. 2005 Mar 23;53(6):1841-56. Review.

Inclusion Criteria:

Women:

1. ≥ 18 years of age
2. diagnosed with gestational diabetes mellitus (GDM) or impaired glucose tolerance of pregnancy (IGTP) according to Canadian Diabetes Association (CDA) criteria
3. being followed within DIP (one of 4 sites)
4. willing and able to give informed consent
5. willing and able to comply with the study protocol

Exclusion Criteria:

Women:

1. with acute or chronic illness other than GDM or IGTP or use of drug (other than insulin) which may affect carbohydrate metabolism, gastrointestinal function or carbohydrate digestion (i.e. crohn's disease, HIV/AIDS, liver disease, kidney disease etc.).
2. known to have type 1 or type 2 DM prior to pregnancy
3. known multi-fetal pregnancy at enrolment
4. ≥ 33 weeks' gestation
5. prescribed oral anti-hyperglycaemic medication
6. insurmountable language barriers

• Canadian Diabetes Association
• Canadian Institutes of Health Research (CIHR)
• Canadian Foundation for Dietetic Research (CFDR)