Table 1. Description of outcome measures assessed at 4 and 5 years.

Outcome measure	Description
Child Language and Learning
Receptive and expressive language	Clinical Evaluation of Language Fundamentals Preschool Second Edition (CELF-P2) Australian Standardised Edition [25]. Direct assessment of child language skills across three subscales: Sentence Structure, Word Structure and Expressive Vocabulary, and a combined Core Language score. Subtest scores reported as age-specific normative scaled scores (m = 10, SD = 3) and Core Language score reported as standard score (m = 100, SD = 15).
Phonological awareness	School Entry Alphabetic and Phonological Awareness Readiness Test (SEAPART) [26]. Direct assessment of pre-literacy skills that are ideally mastered at the point of school entry. Subtest raw scores were assessed across 6 subscales: Syllable Clapping, Syllable Isolation, First Sound Identification, Letter Identification, Name Writing and Rhyme Detection. Total Score assessed as a combined score of all subtests, excluding Rhyme Detection.
Attention and executive function	Two subtests of the NIH Toolbox Early Childhood Cognition Battery (Ages 3–6 years) [27], assessing attention and executive function: Flanker Inhibitory Control & Attention Test and Dimensional Change Card Sort. Both administered to the child as direct assessments on the NIH Toolbox iPad application. Subtest scores examined as standardised age-corrected scores (mean = 100, SD = 15).
Child General and Mental Health
Mental health and behaviour	25-item Strengths and Difficulties Questionnaire (4– to 10-year-old version) [28, 29] assessing Total Difficulties and two domain scores: Internalising Difficulties (combined score of emotional and peer problems) and Externalising Difficulties (combined score of behaviour and attention/hyperactivity). Scores reversed so that higher mean scores indicate fewer problems.
Social Skills	46-item Social Skills Improvement System [30] assessing social skills across 7 domains: Communication, Cooperation, Assertion, Responsibility, Empathy, Engagement and Self-Control. Total score assessed as a combined score of all 7 domains. Assessed at 5-year follow-up only.
Quality of life	21-item Pediatric Quality of Life Inventory (PedsQL) [31] assessing general wellbeing using two subscales: Physical Functioning and Socioemotional Functioning. Higher scores indicate better wellbeing.
Stress (hair cortisol)	Hair cortisol as a measure of physiological stress response over the past 3 months. The hair sample is a minimum length of 3cm, with the total density of the sample equating to approximately half a pencil’s width (30-50mg). Cortisol concentrations are log transformed and negativized so that higher scores indicate lower long-term stress [32].
Global health	Single 5-point item (“poor” to “excellent”) parent-report from the Short Form-6 (SF6) [33], dichotomised into poorer (“poor/fair/good”) versus “very good/excellent” [34].
No dental caries	Direct assessment of early signs of dental decay using ‘lift the lip’ screening to check the outer surface of the child’s top front teeth [35]. Dichotomised into classifications of “healthy (no signs of dental caries)” versus “early/advanced signs of dental caries”.
Not overweight or obese	Direct assessment of height (Invicta Stadiometer) and weight (Tanita HD-315 Digital Scales), used to calculate child age and gender specific BMI (weight/height2) z-scores, dichotomised into international classifications of weight status (“overweight/obese” versus “not overweight or obese (normal weight/underweight)”).
Parenting and Family Relationships
Warm parenting	6-item measure assessing parental warmth. Items rated on a 5-point scale ("never/almost never" to "always/almost always"), drawn from LSAC [36].
Hostile parenting	5-item measure assessing parental hostility. Items rated on a 10-point scale ("not at all" to "all of the time"), drawn from LSAC [36].
Parenting efficacy	4-item Parenting Efficacy scale. Items rated on a 10-point scale ("Not at all how I feel" to "Exactly how I feel") drawn from LSAC, and a single 5-point Parenting Efficacy item assessing mother’s feelings about herself as a parent ("Not very good" to "Very good") drawn from LSAC [36].
Parent-child closeness and conflict	15-item short-form of the Child-Parent Relationship Scale (CPRS) [37, 38]. Parent-reported measure assessing views of their relationship with their child using two subscales: Conflict (scores reversed so that higher scores indicate less conflict) and Closeness (higher scores indicate greater closeness).
Regular meal times	Single 5-point item ("never" to "always"). Study-designed based on Sleep Well Be Well Regular Bedtime item [39].
Regular bedtime	Single 5-point item ("never" to "always"), adapted from the “Sleep Well Be Well study [39].
Regular bed routine	Single 5-point item ("never" to "always"), drawn from the “Sleep Well Be Well study [39].
Child-parent relationship	Single 5-point item (“poor” to “excellent”), study designed based on the single Global Health item drawn from the self-reported Short Form-6 (SF6).
Intimate partner emotional abuse	11-item Emotional Abuse subscale of the Composite Abuse Scales assessing emotionally abusive partner behaviour [40]. Dichotomised as a score of 3 or more indicating the presence of emotional abuse and a score less than 3 indicating no reported emotional abuse.
Maternal Mental Health and Wellbeing
Mental health	Depression, Anxiety and Stress Scales [41]. 21-item measure, rated on a 4-point scale ("not at all" to "most of the time") assessing the negative emotional states of depression, anxiety and tension/stress. Three subscales (7 items each): Depression, Anxiety and Stress. DASS scores were reversed so that higher scores indicate better mental health, ranging from 0–21. Reversed DASS subscale scores were also dichotomised to reflect poorest mental health symptom severity (study-defined as lower 15% of scores according to population reference ranges [42]) versus better mental health (upper 85% of scores).
Wellbeing	Personal Wellbeing Index [43] 8 items assessing satisfaction with specific life domains, rated using a 10-point scale ("no satisfaction at all" to "completely satisfied") and summed for a total score ranging from 1–79 (total scores of 0 and 80 are excluded as response sets).
Quality of life	Assessment of Quality of Life– 8D (AQoL-8D) [44, 45]. 35-item measure assessing health related quality of life. Uses a weighting algorithm to provide a single overall utility-based quality of life measure on a scale of 0–1 (with 1 indicating a better quality of life).
Global health	Single 5-point item self-reported from the Short Form-6 (SF6) [33], dichotomised into poorer (“poor/fair/good”) versus “very good/excellent” [34].
Stress (hair cortisol)	See description for child stress (hair cortisol) above.
Currently employed	Maternal report of current employment (yes/no).
Currently studying	Maternal report of currently studying (yes/no).
Planning future study	Maternal report of planning future study (yes/no).
Self-efficacy	3 items assessing mother’s self-efficacy, drawn from the UK Millennium Cohort [46]. Each item reflected the presence versus absence of self-efficacy and were used to form a single dichotomous item reflecting ‘any lack of self-efficacy’ versus ‘no lack of self-efficacy’.
Doesn’t smoke	Maternal self-report of currently smoking (yes/no).