Full Stage Lay Summary The development of self-regulation, which mainly occurs in the first 4 years of life, is critical in setting an individual's life trajectory, and enabling them, as an adult, to achieve their full potential and best contribution as a member of society. Long-term follow-up of the effectiveness of interventions aimed at improving self-regulation are essential. We plan to measure self-regulation and its underpinnings at 3.5 and 5 years of age in 805 children who have been randomised before birth to one of four groups in a previously funded HRC study (POI.nz) aimed at preventing excessive weight gain in early childhood. The interventions started in pregnancy and continued till 2 years of age, involving advice and support to improve either sleep or feeding and activity, or both in combination; all of which involve self-regulation. If self-regulation is improved & maintained after the interventions finish, this should lead to improved health, educational achievement, work habits and social outcomes, both in childhood as well as adult life.