title: Who is our cohort: recruitment, representativeness, baseline risk and retention in the "Watch Me Grow" study?
abstract: BACKGROUND
  The "Watch Me Grow" (WMG) study examines the current developmental surveillance system in South West Sydney. This paper describes the establishment of the study birth cohort, including the recruitment processes, representativeness, follow-up and participants' baseline risk for future developmental risk.
  
  
  METHODS
  Newborn infants and their parents were recruited from two public hospital postnatal wards and through child health nurses during the years 2011-2013. Data was obtained through a detailed participant questionnaire and linked with the participant's electronic medical record (EMR). Representativeness was determined by Chi-square analyses of the available clinical, psychosocial and sociodemographic EMR data, comparing the WMG participants to eligible non-participants. Reasons for non-participation were also elicited. Participant characteristics were examined in six, 12, and 18-month follow-ups.
  
  
  RESULTS
  The number of infants recruited totalled 2,025, with 50 % of those approached agreeing to participate. Reasons for parents not participating included: lack of interest, being too busy, having plans to relocate, language barriers, participation in other research projects, and privacy concerns. The WMG cohort was broadly representative of the culturally diverse and socially disadvantaged local population from which it was sampled. Of the original 2025 participants enrolled at birth, participants with PEDS outcome data available at follow-up were: 792 (39 %) at six months, 649 (32 %) at 12 months, and 565 (28 %) at 18 months. Participants with greater psychosocial risk were less likely to have follow-up outcome data. Almost 40 % of infants in the baseline cohort were exposed to at least two risk factors known to be associated with developmental risk.
  
  
  CONCLUSIONS
  The WMG study birth cohort is a valuable resource for health services due to the inclusion of participants from vulnerable populations, despite there being challenges in being able to actively follow-up this population.
authors.affiliation: Sydney Children's Hospitals Network, Sydney, Australia. susan.woolfenden@sesiahs.health.nsw.gov.au.|University of New South Wales, Sydney, Australia. susan.woolfenden@sesiahs.health.nsw.gov.au.
authors.forename: Susan
authors.initials: S
authors.lastname: Woolfenden
authors.affiliation: Academic Unit of Child Psychiatry, South West Sydney Local Health District (AUCS), Sydney, Australia.|School of Psychiatry & Ingham Institute, University of New South Wales, Sydney, Australia.|Ingham Institute for Applied Medical Research, Liverpool, Australia.
authors.forename: Valsamma
authors.initials: V
authors.lastname: Eapen
authors.affiliation: Academic Unit of Child Psychiatry, South West Sydney Local Health District (AUCS), Sydney, Australia.|School of Psychiatry & Ingham Institute, University of New South Wales, Sydney, Australia.|Ingham Institute for Applied Medical Research, Liverpool, Australia.
authors.forename: Emma
authors.initials: E
authors.lastname: Axelsson
authors.affiliation: Early Years Research Group, Ingham Institute, Sydney South West Local Health District, Sydney, Australia.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Hendry
authors.affiliation: Ingham Institute for Applied Medical Research, Liverpool, Australia.|Epidemiology Group, Healthy People and Places Unit, South Western Sydney Local Health District, Sydney, Australia.|School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia.
authors.forename: Bin
authors.initials: B
authors.lastname: Jalaludin
authors.affiliation: Olga Tennison Autism Research Centre, La Trobe University, Melbourne, Australia.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Dissanayake
authors.affiliation: Academic Unit of Child Psychiatry, South West Sydney Local Health District (AUCS), Sydney, Australia.|School of Psychiatry & Ingham Institute, University of New South Wales, Sydney, Australia.
authors.forename: Bronwyn
authors.initials: B
authors.lastname: Overs
authors.affiliation: Ingham Institute for Applied Medical Research, Liverpool, Australia.|South Western Sydney Clinical School, University of New South Wales, Sydney, Australia.
authors.forename: Joseph
authors.initials: J
authors.lastname: Descallar
authors.affiliation: Ingham Institute for Applied Medical Research, Liverpool, Australia.|Community Paediatrics, South Western Sydney Local Health District, Sydney, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Eastwood
authors.affiliation: Centre for Disability Research and Policy, Brain & Mind Research Institute, University of Sydney, Sydney, Australia.
authors.forename: Stewart
authors.initials: S
authors.lastname: Einfeld
authors.affiliation: Sydney Children's Hospitals Network, Sydney, Australia.|School of Psychiatry & Ingham Institute, University of New South Wales, Sydney, Australia.|Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia.
authors.forename: Natalie
authors.initials: N
authors.lastname: Silove
authors.affiliation: University of New South Wales, Sydney, Australia.|Ingham Institute for Applied Medical Research, Liverpool, Australia.|Speech Pathology Unit, Liverpool Hospital, Sydney, Australia.
authors.forename: Kate
authors.initials: K
authors.lastname: Short
authors.affiliation: NSW Kids and Families (NSW Health), Sydney, Australia.
authors.forename: Deborah
authors.initials: D
authors.lastname: Beasley
authors.affiliation: Academic Unit of Child Psychiatry, South West Sydney Local Health District (AUCS), Sydney, Australia.|School of Psychiatry & Ingham Institute, University of New South Wales, Sydney, Australia.
authors.forename: Rudi
authors.initials: R
authors.lastname: Črnčec
authors.affiliation: NSW Kids and Families (NSW Health), Sydney, Australia.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Murphy
authors.affiliation: Department of Paediatrics, University of Melbourne, Sydney, Australia.|Developmental Medicine, Royal Children's Hospital, Sydney, Australia.|Murdoch Children's Research Institute, Sydney, Australia.
authors.forename: Katrina
authors.initials: K
authors.lastname: Williams
mesh_terms: D002658:Developmental Disabilities / Q000175:diagnosis* / Q000209:etiology; D057286:Electronic Health Records; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009517:New South Wales; D018579:Patient Selection; D045808:Refusal to Participate / Q000706:statistics & numerical data*; D012307:Risk Factors; D015983:Selection Bias; D011795:Surveys and Questionnaires
keywords: Birth cohort; Participation bias; Recruitment