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).

Conclusions: 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.