Nutrition for gestational diabetes, a pilot study.

Women who express interest in the study, either via online advertisement or from the face to face hospital GDM clinic (described below), will be provided with either an electronic or hard copy of the participant information sheet. Women will then consent to complete an online screening form using REDCap to assess eligibility. For women recruited online, they will be provided with either an electronic or hard copy of the participant information sheet. Following eligibility using REDCap, the research assistant will contact the participant to go over the study, answer any questions, and book them in for their baseline, face to face clinic visit. Following diagnosis of GDM at 24-28 weeks’ gestation, women will attend their routine group counselling session 1-2 days following (usually 28-29 weeks’ gestation). At this visit, a research assistant will enrol eligible and consenting women. Participants will be asked to complete a short questionnaire (demographic information and pregnancy history) and baseline measures: 1) non-fasting blood test; 2) current height and weight; 2) blood pressure; and 4) a 24-hour dietary recall (24 HDR) interview using a web-based dietary assessment tool ASA24®. After this, women will be randomised to one of two groups: control/standard care or intervention. Up to two days after enrolment, a study dietitian will follow up with women randomised to the intervention group via telephone or zoom where they will receive a 30-minute individual counselling session with the study dietitian incorporating behaviour change techniques. The study dietitian will review the 24 HDR and develop tailored advice for each participant (15 minutes). They will receive an individual counselling session via telephone or zoom with the dietitian on how to increase intake of whole fruits, vegetables, and nuts, modify cooking oils, and decrease intake of ultra-processed foods. This session will be a complement rather than a replacement of the group counselling sessions. Women who ask for clarification on material covered in the standard GDM counselling session will be referred to the diabetes educator to avoid confounding. The study dietitian will maintain regular contact with intervention participants via telephone, SMS, or email to ensure compliance with the dietary intervention. Following the individual counselling session, the study dietitian will contact participants on a fortnightly basis. Compliance will be measured by self-report; the proportion of women meeting personalised targets for fruit, vegetable and nuts, modifications to cooking oils, and reduction in servings of ultra-processed foods will be determined from the number of current daily servings reported. To aid in behaviour change, within the counselling session, the study dietitian (who will be trained and supported by a health psychologist), will incorporate the use of behaviour change techniques drawn from the Behaviour Change Technique Taxonomy (15 minutes). The behaviour change technique clusters to be used in this session include shaping knowledge, antecedents, goals and planning, repetition and substitution, and social support. During this coaching session, the dietitian will use the behaviour change technique clusters of feedback and monitoring, shaping knowledge, antecedents, goals and planning, repetition and substitution, and social support. Specifically, the dietitian will: 1) review goals, action plans, antecedents, dietary behaviours (including habit reversals and substitutions) and outcomes; 2) assist women to revise their goals, action plans, dietary behaviours and restructure their environment if needed; 3) provide feedback on diet behaviours; 4) provide further practical advice on how to improve diet, and 5) provide support by recognising and complimenting positive changes, normalising any difficulties associated with dietary change or behaviour relapse and encouraging women to continue in their efforts. Discussion will also include identifying people within their network that can be emotional and/or practical supports in their efforts to establish a healthy diet. Women allocated to the intervention group will receive health coaching advice again at 32-34 weeks' gestation to strengthen uptake. A trained phlebotomist will collect a maternal venous blood sample (up to 14 ml) according to standard SOP for venepuncture, at baseline and at the end of the intervention period. For women who choose not to have a blood sample, the study researcher will follow up on reasons for this (self reported, no specific checklist). Feasibility will be assessed by proportion of women having the blood sample taken, and a written description for common reasons among women where a sample was not taken.