More than 50% of pregnant women are considered to have a BMI that is classified as overweight or obese when they present for antenatal care. Overweight and obesity in pregnancy is associated with complications and poorer health outcomes for mothers and their babies, as well as risk for excessive gestational weight gain and postpartum weight retention, increasing the likelihood of long-term obesity for these women. There is also evidence that excess maternal weight and weight gain in pregnancy is associated with obesity in the offspring from early childhood through to adolescence. There is an urgent need for simple, effective interventions targeting lifestyle which can be delivered during routine healthcare.

The overall aim of this study is to pilot test the delivery of a brief, habit-based weight management intervention, 'Healthy Habits In Pregnancy and Beyond', for pregnant women with overweight and obesity (body mass index between 25.0 & <38.0 kg/m2) in early pregnancy, to gather preliminary information on the intervention and to establish the feasibility and acceptability of delivering this intervention into routine antenatal care and existing antenatal care pathways across four geographical locations in Northern Ireland and the Republic of Ireland.

This study is a two-arm randomised controlled feasibility study. Healthcare staff in four partner sites will be trained in introducing the study to the target sample and in delivering the intervention. 80 women will be recruited and randomised to control (n=40) or intervention group (n=40) (20 at each site). Women randomised to the intervention group will receive a brief intervention to encourage the development of ten healthy habits in relation to diet, physical activity and weight management, plus their local routine antenatal care. The intervention will be delivered by a designated midwife at each site or a member of the research team, and is aimed to be integrated into appointments already attended by women as part of routine antenatal care. Women randomised to the control group will receive their local routine antenatal care.

The primary objective of the feasibility study is to provide a decision on whether to proceed to a full-scale, multicentre RCT.

The two-arm randomised controlled feasibility study will:

1. Assess the numbers of eligible pregnant women accessing the healthcare services at each partner healthcare site;
2. Assess screening, recruitment and attrition rates;
3. Assess willingness of healthcare staff to recruit women and deliver the HHIPBe intervention as part of routine antenatal clinical care;
4. Assess indicators of engagement with the intervention by women (self-reported logbooks/ app data/ qualitative post-intervention interviews);
5. Assess the acceptability of randomisation to a 'usual care' group and women's views on completion of study measures at each time-point;
6. Assess the acceptability of the intervention to women;
7. Assess fidelity of intervention implementation across each partner site i.e. was HHIPBe delivered as intended;
8. Trial the outcome measures that would be used in a full trial of HHIPBe (and gather data to inform a power calculation for a full trial) including assessment of: GWG, habit-formation and diet and activity behaviours up to 6 weeks postpartum; and health economics measures, alongside an exploration of the potential for data linkage to maternal and neonatal outcomes in each jurisdiction.

Inclusion Criteria:

• Pregnant Women.
• Body Mass Index between ≥25.0 kg/m2 and <38.0 kg/m2.
• Primiparous or Multiparous.
• Women capable of providing informed consent and of providing consent on behalf of their child.

Exclusion Criteria:

• Twin or multiple pregnancies.
• Insufficient English to understand intervention and written materials.
• Nutritional complications i.e. previous or current eating disorder, following a special diet, in receipt of specialist dietary advice.
• Pregnancy not viable as determined by the patient's clinical team.
• Have been referred to another weight management service by their clinical team during pregnancy that is not part of routine antenatal care.

Due to the nature of the trial, it will not be possible to blind participants or intervention facilitators to group allocation. Researchers involved in collecting outcome data will not have access to details of group allocation and we will attempt to retain this blinding throughout. Participants will be asked not to discuss their group allocation with the researchers. Fidelity of blinding will be assessed.