North-South Gradients in Adverse Birth Outcomes for First Nations and Others in Manitoba, Canada.

OBJECTIVE: to determine the relationship of north-south place of residence to adverse birth outcomes among First Nations and non-First Nations in Manitoba, Canada, a setting with universal health insurance. STUDY DESIGN: Live birth records (n=151,472) for the province of Manitoba, Canada 1991-2000 were analyzed, including 25,743 First Nations and 125,729 non-First Nations infants. North-south and rural-urban residence was determined for each birth through geocoding. RESULTS: Comparing First Nations to non-First Nations, crude rates in North (and South) were: 7.0% versus 8.4% (9.3% versus 7.5%) for preterm birth; 6.1% versus 8.4% (8.7% versus 10.0%) for small-for-gestational-age birth, 4.2% versus 6.5% (6.2% versus 5.7%) for low birth weight, and 20.6% versus 13.7% (17.0% versus 11.0%) for large-for-gestational-age birth; and mortality per 1000 - neonatal 3.2 versus 6.2 (3.8 versus 3.3), post-neonatal 6.4 versus 6.4 (5.8 versus 1.5), and infant 9.5 versus 12.6 (9.6 versus 4.8). Adjusting for observed maternal and infant characteristics and rural versus urban residence, the North was high risk for large-for-gestational-age birth for both First Nations and non-First Nations. First Nations' risk of preterm, small-for-gestational-age and low birth weight was lowest in the North, but for non-First Nations, the North was lower only for small-for-gestational-age. First Nations mortality indicators were similar North to South, but for non-First Nations, the North was high risk. CONCLUSION: North-South place of residence does matter for adverse birth outcomes, but the effects may differ by ethnicity and could require different intervention strategies.