The goal of this randomised controlled trial is to test the effectiveness of a mobile instant messaging-based lifestyle intervention in pregnant women at risk of gestational diabetes

Gestational diabetes mellitus (GDM) is one of the most common medical conditions during pregnancy, affecting about 1 in 7 live births worldwide. There remains a lack of proven preventive strategies for GDM that could be readily adopted in clinical practice. Recent studies have suggested that lifestyle intervention delivered via mobile phone could help pregnant women prevent GDM, but more evidence is needed. This study aims to test a mobile instant messaging-based lifestyle intervention for GDM prevention in pregnant women at risk of GDM.

Inclusion Criteria:

1. Ethnic Chinese singleton pregnant woman in <14 weeks of gestation

2. Aged 18 years or above

3. Own a mobile phone with an instant messaging app

4. Not participating in similar trials on diabetes or lifestyle modifications

5. Have at least one of the following risk factors for GDM:

   • Age ≥35 years at the expected date of delivery
   • Body mass index (BMI) ≥ 25 kg/m2 pre-pregnancy or in the first trimester
   • Family history of diabetes in first-degree relative
   • Previous GDM or delivered a baby with birthweight ≥4 kg

Exclusion Criteria:

• Pre-existing diabetes or other medical conditions that may affect metabolism (e.g., thyroid disorders) or psychiatric disorders