The IDEAL study: investigation of dietary advice and lifestyle for women with borderline gestational diabetes: a randomised controlled trial - study protocol.

BACKGROUND: The Australian Carbohydrate Intolerance Study in Pregnant Women (ACHOIS) showed that treatment of pregnant women with mild gestational diabetes mellitus is beneficial for both women and their infants. It is still uncertain whether there are benefits of similar treatment for women with borderline gestational diabetes.This trial aims to assess whether dietary and lifestyle advice and treatment given to pregnant women who screen for borderline gestational diabetes reduces neonatal complications and maternal morbidities.

METHODS/DESIGN: Multicentre, randomised controlled trial.

INCLUSION CRITERIA: Women between 240 and 346 weeks gestation with a singleton pregnancy, a positive oral glucose challenge test (venous plasma glucose ≥7.8 mmol/L) and a normal oral 75 gram glucose tolerance test (fasting venous plasma glucose <5.5 mmol/L and a 2 hour glucose <7.8 mmol/L) with written, informed consent.Trial entry and randomisation: Women with an abnormal oral glucose tolerance test (fasting venous plasma glucose ≥5.5 mmol/L or 2 hour glucose ≥7.8 mmol/L) will not be eligible and will be offered treatment for gestational diabetes, consistent with recommendations based on results of the ACHOIS trial. Eligible women will be randomised into either the 'Routine Care Group' or the 'Intervention Group'.Study groups: Women in the 'Routine Care Group' will receive routine obstetric care reflecting current clinical practice in Australian hospitals. Women in the 'Intervention Group' will receive obstetric care, which will include dietary and lifestyle advice, monitoring of blood glucose and further medical treatment for hyperglycaemia as appropriate.Primary study outcome: Incidence of large for gestational age infants.

SAMPLE SIZE: A sample size of 682 women will be sufficient to show a 50% reduction in the risk of large for gestational age infants (alpha 0.05 two-tailed, 80% power, 4% loss to follow up) from 14% to 7% with dietary and lifestyle advice and treatment.

DISCUSSION: A conclusive trial outcome will provide reliable evidence of relevance for the care of women with borderline glucose intolerance in pregnancy and their infants.

TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry - ACTRN12607000174482.