The overarching objective of this research is to detect poor growth and delayed development early in childhood by developing an automated growth-screening algorithm. The screening algorithm will be created using cohort data and piloted for feasibility and acceptability in Tower Hamlets. The ultimate goals are to detect linear growth failure and delayed development early to identify two groups of children: first, children with serious underlying medical disorders, in whom earlier diagnosis and management would improve clinical outcomes; and second, children whose poor growth and/or delayed development is a manifestation of socioeconomic disadvantage, in whom targeted pre-school interventions may improve long term health and education outcomes.

Aim 1, Pilot an automated growth screening algorithm in Tower Hamlets

600 pre-school children at age 2-2.5 years will be enrolled into a pilot screening programme, following written informed parental consent. Children will be identified when they have their 2-2.5 year contact as part of the Healthy Child Programme. As per standard care, measures will be taken of the child's height using a stadiometer and weight using digital weighing scales. In addition to these measurements will be the child's head circumference, their height using a phone App and a record taken of previous anthropometric data including birthweight from the Personal Health Record. Parents' heights will also be recorded where possible. Next, families will be offered an additional height measurement at 3-3.5 years in the community, which is not currently part of standard care. Child height will then be recorded as part of the routine National Child Measurement Programme at 4-5 years of age, and linked to primary care data, enabling the growth-screening algorithm to be applied to these three data-points (2-2.5 years, 3-3.5 years and 4-5 years). At each height measurement the study team will identify the 2% of children with the poorest growth, in whom prior studies show a high prevalence (30-40%) of medical disorders and contact parents to offer referral to the paediatric endocrinology clinic at the Royal London Hospital. The study team will evaluate acceptability and feasibility of the screening and referral process, using parental and healthcare professional questionnaires. There will be an evaluation of the uptake by calculating the proportions screened, referred, investigated in clinic and diagnosed with medical disorders.

Focus group discussions will also be held with caregivers (one in English language and one in Sylheti) and with Health Visitors, to get an idea of how they feel about screening and identify potential barriers to a larger scale roll out.

Aim 2, Generate pilot data to investigate the best indicators to detect poor school readiness and/or developmental problems in early childhood.

As part of routine care, each child's development will be assessed using both the caregiver and professional components of the The Ages & Stages Questionnaire (ASQ-3). Following the 2-2.5 year contact, a subset of children (n = 150) will be invited to attend a separate appointment in the community to have a more detailed developmental assessment to measure gross motor, fine motor, social, language, visual-spatial and practical reasoning skills, conducted or supervised by a child psychologist. These data will be used to conduct sensitivity analyses to test the hypothesis that linear growth failure either alone or in combination with additional factors identifies children with reduced neurodevelopment, who are therefore at risk of poor school attainment.

Inclusion Criteria:

• Children aged 2-2.5 years, who live in Tower Hamlets and whose caregiver(s) are willing to provide written informed consent

Exclusion Criteria:

• The caregiver does not provide written informed consent
• The child is not able to stand for an accurate height measurement

Children randomly chosen from London borough of Tower Hamlets, based on Health Visitor records. All children will have height and weight measured as part of standard care by a Health Visitor or nursery nurse in the community, and caregivers are asked to complete a development questionnaire at age 2- 2.5 years as standard. Caregivers will be approached about taking part in the study and given information about what this involves.