A prospective cohort study of pregnancy risk factors and birth outcomes in Aboriginal women.

backgroundAboriginal women have been identified as having poorer pregnancy outcomes than other Canadian women, but information on risk factors and outcomes has been acquired mostly from retrospective databases. We compared prenatal risk factors and birth outcomes of First Nations and Métis women with those of other participants in a prospective study.

methodsDuring the 12-month period from July 1994 to June 1995, we invited expectant mothers in all obstetric practices affiliated with a single teaching hospital in Edmonton to participate. Women were recruited at their first prenatal visit and followed through delivery. Sociodemographic and clinical data were obtained by means of a patient questionnaire, and microbiological data were collected at 3 points during gestation: in the first and second trimesters and during labour. Our primary outcomes of interest were low birth weight (birth weight less than 2500 g), prematurity (birth at less than 37 weeks' gestation) and macrosomia (birth weight greater than 4000 g).

resultsOf the 2047 women consecutively enrolled, 1811 completed the study through delivery. Aboriginal women accounted for 70 (3.9%) of the subjects who completed the study (45 First Nations women and 25 Métis women). Known risk factors for adverse pregnancy outcome were more common among Aboriginal than among non-Aboriginal women, including previous premature infant (21% v. 11%), smoking during the current pregnancy (41% v. 13%), presence of bacterial vaginosis in midgestation (33% v. 13%) and poor nutrition as measured by meal consumption. Although Aboriginal women were less likely than non-Aboriginal women to have babies of low birth weight (odds ratio [OR] 1.46, 95% confidence interval [CI] 0.52-4.15) or who were born prematurely (OR 1.45, 95% CI 0.57-3.72) and more likely to have babies with macrosomia (OR 2.04, 95% CI 1.03-4.03), these differences were lower and statistically nonsignificant after adjustment for smoking, cervicovaginal infection and income (adjusted OR for low birth weight 0.85, 95% CI 0.19-3.78; for prematurity 0.90, 95% CI 0.21-3.89; and for macrosomia 2.12, 95% CI 0.84-5.36).

interpretationAfter adjustment for potential confounding factors, we found no statistically significant relation between Aboriginal status and birth outcome.