Abstract Background Despite improved survival of extreme preterm infants (<29 weeks’ gestation), neurodevelopmental impairment (NDI) remains high. Certain sociodemographic characteristics (SDC) and limited family resources are known to adversely affect children health and development, particularly those born preterm. There is a dearth of recent data from large cohorts examining the impact of social determinants of health on the neurodevelopment of preterm children. Objectives (1) to describe SDC and family composition in a population-based cohort of extreme preterm children using the Canadian Neonatal Follow Up Network (CNFUN) database; (2) to develop a logistic regression model examining the association of significant NDI (sNDI any of: CP ≥ GMFCS stage 3, Bayley III < 70 in any domain, deafness requiring aids, or bilateral blindness) with SDC using a unique family descriptor. Design/Methods A retrospective review of a national cohort of extreme preterm infants (230 -286 weeks) born between April 2009 and December 2018. We included children who had neurodevelopmental assessment at 18-24 month corrected age at a CNFUN participating Centre. We compared SDC of infants and caregivers and family descriptors (moderating variables) between children with no NDI and those with any NDI and sNDI. Multivariate logistic regression models were developed in two steps to evaluate the effect of SDC (Model 1) and family composition (Model 2) on the primary outcome of sNDI. GEE was used to account for clustering by multiples and within site. Results Out of 10833 eligible infants, 6219 (57%) were included. Of those, 3412 (55%) had no NDI and 2807 (45%) had any NDI. sNDI accounted for 17% of the cohort and 37% of those with NDI. Comparison of the SDC and family descriptors between the three groups are shown in Table 1. On multivariate analysis using SDC, infant’s gestational age and male sex, and primary caregiver’s ethnicity and level of education were independently associated with sNDI. Immigration and employment status were associated with sNDI when family descriptors were added to the first model (Table 2). Conclusion In this national cohort, half of extreme preterm children developed NDI and 1 in 7 had sNDI. There were differences in sociodemographic and family characteristics between those with and without sNDI. The degree of prematurity and caregiver’s education, employment and immigration status were independently associated with sNDI in those children. Future research is needed to determine what interventions and support to benefit those children at risk.