Background/Project Description: There is a growing interest in the contribution of late preterm (34 – 36 week gestational age (GA)) birth to neonatal morbidity and mortality. Late preterm infants have an increased incidence of both respiratory and non- respiratory complications over the first year of life. Rates of prematurity as well as morbidity/mortality in infancy are higher in lower socioeconomic status (SES) groups but how GA and SES interact is relatively unexplored.

Methods/Participant Population: A retrospective cohort study was undertaken utilizing anonymized data housed at the Manitoba Centre for Health Policy (MCHP). A population-based cohort of infants born at 34 to 41 weeks of GA was assembled; individual and area-level income information was used to develop SES groups. Outcomes studied included diagnoses received during the birth hospitalisation, neonatal and post-neonatal admissions. Regression models were constructed to explore the effects of GA and SES as well as control for multiple perinatal variables. Appropriate approvals and safeguards for data privacy were maintained.

Results: GA and SES exerted a gradient effect on morbidity, which persisted after controlling for multiple confounding variables. The effect of GA was strongest during the birth hospitalisation but persisted throughout the first year with increased morbidity evident with each week of decreasing GA. The detrimental association of low SES with morbidity increased in effect size throughout the first year surpassing that of GA for post-neonatal admissions. An interaction effect of maternal diabetes, respiratory morbidity and SES was suggested and merits further investigation. Neonatal stays of 3 days or longer negated the association of GA with readmission within the first 28 days; in addition shorter stay infants had the highest risks of readmission at 37 weeks as compared to the late preterm gestations.

Conclusions: The consistent associations between poverty, prematurity and morbidity require both further study and attention. Attention to the neonatal health of both late preterm and term infants is important due to their large numbers and population impact. The added risk of poverty merits urgent and multifaceted interventions to lay the groundwork for healthy childhood and long-term success.