Neighbourhood socio-economic status and spontaneous premature birth in Alberta.

OBJECTIVE To evaluate a possible association between neighbourhood socio-economic status and spontaneous premature birth in Alberta births. METHODS The study design was a retrospective cohort of all births in Alberta for the years 2001 and 2006. The primary outcome was spontaneous preterm birth at <37 weeks gestation. Neighbourhood socio-economic status was measured by the Pampalon Material Deprivation Index for each Statistics Canada census dissemination area. Births were linked to dissemination area using maternal postal codes. RESULTS The analysis comprised 73,585 births, in which the rate of spontaneous preterm delivery at <37 weeks was 5.3%. The rates of spontaneous preterm delivery for each neighbourhood socio-economic category ranged from 4.9% (95% CI 4.5%-5.2%) in the highest category to 6.3% (95% CI 6.0%-6.7%) in the lowest (p<0.001). After controlling for smoking, parity, maternal age and year, we found that women living in the highest socio-economic status neighbourhoods had an adjusted spontaneous preterm birth rate of 5.1% (95% CI 4.7%-5.5%) compared to 6.0% (95% CI 5.6%-6.4%) for women living in the lowest (p=0.003). CONCLUSION This study documented a modest increase in the risk of spontaneous preterm birth with low socio-economic status. The possibility of confounding bias cannot be ruled out.