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

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

The Effect of a Low GI Diet on Maternal and Neonatal Markers of Glycaemic Control and Postpartum Diabetes Risk SUBSTUDY The Effect of a Low GI Diet on Postpartum Markers of Oxidation in Breast Milk of Women With Gestational Hyperglycaemia

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

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. The antioxidant capacity of BM in women with GDM will also be compared with that of women without GDM. Hypotheses: 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. SUB-STUDY: 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. BM of women with GDM will have lower antioxidant capacity than that of women without GDM.

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 Hypotheses: 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. BM of women with GDM will have lower anti-oxidant capacity than that of women without GDM.

"glycaemic index", "glycemic index", hyperglycaemia, hyperglycemia, pregnancy, "dietary intervention", "education evaluation", antioxidant, "Impaired Glucose Tolerance of Pregnancy", "Gestational Diabetes Mellitus", "Breast Milk"

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.

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.

MAIN STUDY: Percentage of postprandial self monitored blood glucose (SMBG) values within the target range

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.

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.

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)

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.

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.

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.

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.

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.

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.

Difference in Oxygen Radical Absorbance Capacity (ORAC) of plasma measured in venous serum at randomization and 4 weeks.

MAIN STUDY: Post-partum serum glucose concentration 2 hours after consumption of 75g oral glucose (2hrPC serum glucose).

Venous serum glucose concentration 2 hours after consumption of 75g oral glucose (oral glucose tolerance test).

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.

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.

Difference between maternal body weight at randomization and last body weight measured before delivery divided by the number of weeks between the measurements.

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.

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.

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.

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

Difference between infant ultrasound measurements (Bi-parietal diameter, head circumference, abdominal circumference, and femur length) from baseline to delivery.

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.

Socio-demographic factors previously identified in the literature as affecting infant feeding practices; including access to breastfeeding education while in hospital.

Difference in the incidence and severity of maternal symptoms present from baseline to 6-8 weeks postpartum using a standardised questionnaire.

Participant reactions and opinions on baseline education class using a face-validated, pre-tested questionnaire.

Difference in participant knowledge of GI from randomization pre-education class) to 6-8 weeks after delivery using a face-validated, pre-tested questionnaire.

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.

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.

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.

MAIN STUDY Inclusion Criteria: Women: ≥ 18 years of age diagnosed with gestational diabetes mellitus (GDM) or impaired glucose tolerance of pregnancy (IGTP) according to Canadian Diabetes Association (CDA) criteria being followed within DIP (one of 4 sites) willing and able to give informed consent willing and able to comply with the study protocol Exclusion Criteria: Women: 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.). known to have type 1 or type 2 DM prior to pregnancy known multi-fetal pregnancy at enrolment ≥ 33 weeks' gestation prescribed oral anti-hyperglycaemic medication insurmountable language barriers SUB-STUDY control group (women without GDM) Same as for Main study except absence of GDM

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