Primary prevention of gestational diabetes for women who are overweight and obese: a randomised controlled trial

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Gestational Diabetes Mellitus (GDM) has well recognised adverse health implications for the mother and her newborn that are both short and long term. Obesity is a significant risk factor for developing GDM and the prevalence of obesity is increasing globally. It is a matter of public health importance that clinicians have evidence based strategies to inform practice and currently there is insufficient evidence regarding the impact of dietary and lifestyle interventions on improving maternal and newborn outcomes. The primary aim of this study is to measure the impact of a telephone based intervention that promotes positive lifestyle modifications on the incidence of GDM. Secondary aims include: the impact on gestational weight gain; large for gestational age babies; differences in blood glucose levels taken at the Oral Glucose Tolerance Test (OGTT) and selected factors relating to self-efficacy and psychological wellbeing. A randomised controlled trial (RCT) will be conducted involving pregnant women who are overweight (BMI >25 to 29.9 kg/m^2) or obese (BMI >30kg/m^2), less than 14 weeks gestation and recruited from the Barwon South West region of Victoria, Australia. From recruitment until birth, women in the intervention group will receive a program informed by the Theory of Self-efficacy and employing Motivational Interviewing. Brief (less than 5 minute) phone contact will alternate each week with a text message/email and will involve goal setting, behaviour change reinforcement with weekly weighing and charting, and the provision of health information. Those in the control group will receive usual care. Data for primary and secondary outcomes will be collected from medical record review and a questionnaire at 36 weeks gestation. Evidence based strategies that reduce the incidence of GDM are a priority for contemporary maternity care. Changing health behaviours is a complex undertaking and trialling a composite intervention that can be adopted in various primary health settings is required so women can be accessed as early in pregnancy as possible. Using a sound theoretical base to inform such an intervention will add depth to our understanding of this approach and to the interpretation of results, contributing to the evidence base for practice and policy.